Irregularities at the Base of the Proximal Phalanges

There can be cortical indistinctness at the base of the proximal phalanges in normal subjects that can mimic erosions seen in rheumatoid arthritis. These are not a reliable sign of early rheumatoid arthritis in the absence of juxtaarticular osteoporosis or changes in the metacarpal heads.

References

Stelling CB, Keats MM, Keats TE. Irregularities at the base of the proximal phalanges: false indicator of early rheumatoid arthritis. AJR Am J Roentgenol. 1982 Apr;138(4):695-8.

Dilated Rete Testis

Dilatation of the rete testes is a benign condition that is most commonly seen in older men (older that 60) and is commonly associated with epididymal abnormalities (e.g., spermatocele).

On ultrasound, there are multiple, small, cystic tubular structures within the rete testis. On MRI, there are serpiginous tubular structures in the rete testis that are hypointense on T1-weighted images, hyperintense on T2-weighted images, and don't enhance.

References

Kim W, Rosen MA, Langer JE, Banner MP, Siegelman ES, Ramchandani P. US MR imaging correlation in pathologic conditions of the scrotum. Radiographics. 2007 Sep-Oct;27(5):1239-53.

Deep Infrapatellar Bursa

The deep infrapatellar bursa (D) is a V-shaped structure with its apex located between the inferior patellar tendon (PT) and anterior tibial margin. Its crotch opens into a process of the Hoffa fat pad called the fat apron. The bursa may extend laterally beyond the margin of the patellar tendon in 70%-100% of cases and medially to the medial margin of the patellar tendon in up to 45% of cases.

No communication has been reported between this bursa and the articular cavity of the knee. Just anterior to the patellar tendon is another bursa, the superficial infrapatellar bursa (S).

Fluid can be observed in the deep infrapatellar bursa during MR imaging in a variety of conditions, including overuse (e.g., runners and jumpers), ankylosing spondylitis, infection, gout, trauma, and Osgood–Schlatter disease. Between 20%-40% of asymptomatic subjects may also demonstrate fluid in the deep infrapatellar bursa.

Deep infrapatellar bursitis presents clinically as anterior knee pain near the insertion of the patellar tendon

References

Viegas FC, Aguiar RO, Gasparetto E, Marchiori E, Trudell DJ, Haghighi P, Resnick D. Deep and superficial infrapatellar bursae: cadaveric investigation of regional anatomy using magnetic resonance after ultrasound-guided bursography. Skeletal Radiol. 2007 Jan;36(1):41-6.

Focal Hepatic Hot Spot Sign

The focal hepatic hot spot sign can be seen on ^99mTc sulfur colloid "liver and spleen" scans as a focal area of increased uptake in segment IV of the liver.

It is typically seen in superior vena cava obstruction, due to portosystemic venous shunting between the superior vena cava and the left portal vein via the internal mammary and paraumbilical veins (this can also be seen on CT).

Other conditions can cause increased uptake anywhere in the liver, including segment IV. These include liver abscesses, hemangioma, focal nodular hyperplasia, and hepatocellular carcinoma. Budd-Chiari syndrome typically causes focal uptake in the caudate lobe.

References

Dickson AM. The focal hepatic hot spot sign. Radiology. 2005 Nov;237(2):647-8.

Fibrous Ring Lesions in Metacarpal Heads

I'd been seeing these rounded lucencies with well-defined, thin, sclerosed borders in metacarpal heads for a while, and almost called one an erosion in a patient. Turns out Keats (eighth edition, Fig 6-321) calls these ring lesions, probably fibrous and apparently of no clinical significance. I have not found peer-reviewed confirmation of this, however.

Shin Splints vs Stress Fracture on MRI

Shin splints and stress fractures fall at opposite poles of the same spectrum. MRI can help differentiate the two.

Shin splints present on T1-weighted images as intermediate signal within the deep subcutaneous tissues overlying the medial tibial cortex, intermediate signal within the cortex, or eccentric hypointense marrow. STIR images may show periosteal edema in direct contact with medial tibial cortex with anteromedial to posteromedial extension to the origin of soleus. The marrow may be hyperintense anteriorly or posteromedially, and there may be intermediate-to-hyperintense focus within the anterior tibial cortex.

Stress fractures, on the other hand, may show interruption of the cortex posteromedially, as well as a wide high signal in the marrow on STIR images.

Delayed images on bone scan will show activity along the posteromedial border of the tibia (i.e., soleus muscle origin). Perfusion and blood pool images will be normal.

The T1-weighted image here shows edema along the subcutaneous tissues anteromedial to the tibia. We went kind of overboard with the STIR, but you should be able to make out the edema-like signal corresponding to the T1 findings. No marrow edema was seen and no fracture could be identified.

References

Aoki Y, Yasuda K, Tohyama H, Ito H, Minami A. Magnetic resonance imaging in stress fractures and shin splints. Clin Orthop Relat Res. 2004 Apr;(421):260-7.

Ivory Epiphysis

Ivory epiphysis refers to a uniformly dense epiphysis that can be a normal variant in the hands of children, usually in the distal phalanges and the middle phagalnx of the small finger. It is seen in up to 8% of boys and up to 4% of girls.

Ivory epiphyses can also occur in pathological states, such as growth retardation, renal osteodystrophy, type 1 trichorhinophalangeal dysplasia and Cockayne syndrome, where they may be indistinguishable from the normal variant, and in Thiemanns disease, where the proximal and middle phalanges (most commonly the middle finger) are usually involved.

This should not be confused with the ivory phalanx sign of psoriatic arthritis.

References

Castriota-Scanderbeg A and Dallapiccola B. Abnormal skeletal phenotypes: from simple signs to complex diagnoses. Springer (2005).

Thyroid Stunning

Thyroid stunning is the temporary impairment of thyroid tissue after a diagnostic ¹³¹I dose greater than 3 mCi that has been said to decrease the final absorbed dose in subsequent ¹³¹I radioablation therapy, leading to decreased efficacy of ablation.

More recent reports have cast doubt on the existence of this phenomenon, leading some to suggest that its impact has been overemphasized. Others strongly defend the existence of the phenomenon. We take the conservative approach at our institution and use ¹²³I for diagnostic purposes as much as is possible.

References

• Dam HQ, Kim SM, Lin HC, Intenzo CM. 131I therapeutic efficacy is not influenced by stunning after diagnostic whole-body scanning. Radiology. 2004 Aug;232(2):527-33.
• Gerard SK, Dam HQ. Stunning with 131I diagnostic whole-body imaging of patients with thyroid cancer. Radiology. 2005 Mar;234(3):972-3; author reply 973-4.
• Morris LF, Waxman AD, Braunstein GD. The nonimpact of thyroid stunning: remnant ablation rates in 131I-scanned and nonscanned individuals. J Clin Endocrinol Metab. 2001 Aug;86(8):3507-11.

The Infrahoffatic Recess

The infrahoffatic recess is a synovium-lined cleft along the inferoposterior aspect of the infrapatellar (Hoffa) fat pad that demonstrates fluid intensity.

The main differential considerations include infrahoffatic ganglia or fluid-like tumors. The infrahoffatic recess is differentiated from these by its location within the midsagittal plane between the alar folds. It is typically between 5 mm - 15 mm. It may have a linear (most common), pipe-shaped, ovoid, or globular configuration.

Ganglions are usually lobulated and/or septated. Tumors that may mimic the infrahoffatic recess include fibroma of the patellar tendon sheath or a glomus tumor, but these are uncommon.

References

• Aydingöz U, Oguz B, Aydingöz O, Bayramoglu A, Demiryürek D, Akgün I, Uzün I. Recesses along the posterior margin of the infrapatellar (Hoffa's) fat pad: prevalence and morphology on routine MR imaging of the knee. Eur Radiol. 2005 May;15(5):988-94.
• Vahlensieck M, Linneborn G, Schild H, Schmidt HM. Hoffa's recess: incidence, morphology and differential diagnosis of the globular-shaped cleft in the infrapatellar fat pad of the knee on MRI and cadaver dissections. Eur Radiol. 2002 Jan;12(1):90-3.

Gastric Emptying in Patients with Laparoscopic Banding

We had a patient referred for a gastric emptying study following laparoscopic banding. The questions that came up were: Where should we put the region-of-interest and What values would count as normal.

Tiktinsky et al, studied gastric emptying in 16 asymptomatic patients following laparoscopic banding by placing their region-of-interest around the gastric pouch and around the whole stomach. They report values for the gastric pouch. Hladik et al studied gastric emptying in 6 patients prior to and following laparoscopic banding, but don't specify where their region-of-interest was placed.

Regarding the second question, Hladik et al, using a solid meal, found an average T_1/2 of 24 minutes or so for obese patients pre-operatively. Post-operative patients who had good weight loss had delayed gastric emptying with T_1/2 of 53 minutes. Patients who didn't have significant reduction in body weight, on the other hand, didn't show prolonged gastric emptying times.

Tiktinsky et al used semi-solid meals and found a T_1/2 of about 37 minutes in postoperative patients, compared to 23 minutes or so for a different group of obese patients prior to surgery.

So it seems that the region-of-interest should be placed around the gastric pouch and that prolonged emptying with T_1/2 of 50 minutes or so should be expected for solid meals in patients with good weight loss, and about 20 or so for those without significant weight loss. Tiktinsky et al's study was not longitudinal, but their study suggests that a T_1/2 of about 40 minutes should be expected in asymptomatic patients using a semi-solid meal.

We ended up putting regions-of-interest around the gastric pouch and the total stomach. The T_1/2 values for the two were nearly the same (about 40).

References

• Hladik P, Vizda J, Mala E, Zadak Z, Hroch T. The contribution of gastric emptying scintigraphy to the treatment of obesity with gastric bandage--preliminary results. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2008 Jun;152(1):125-8.
• Tiktinsky E, Lantsberg L, Lantsberg S, Mizrahi S, Agranotvich S, Friger M, Kirshtein B. Gastric emptying of semisolids and pouch motility following laparoscopic adjustable gastric banding. Obes Surg. 2009 Sep;19(9):1270-3.

Os Intermetatarseum

An os intermetatarseum is found between the bases of the first and second metatarsals. It varies in shape and size from a small rounded ossicle to a fusiform one half as long as the adjacent metatarsal. It may be a distinct ossicle or attached to the first or second metatarsal or to the medial cuneiform. It is found in about 1.5% of the population (the case shown here was found after going through about 160 foot x-rays).

Os intermetatarseum is usually asymptomatic, but it can fracture or be associated with a varus deformity of the first metatarsal and with hallux valgus.

For such a tiny ossicle, the origin of the os intermetatarseum is controversial. It has been variously described as a vestigial sixth digit, a sesamoid, or a developmental variant of the medial cuneiform. In support of the first two, it can be found in an accessory tendon of the first dorsal interosseous muscle or in the tendon of a vestigial plantar interosseous tendon.

References

Lawson JP. Symptomatic radiographic variants in extremities. Radiology. 1985 Dec;157(3):625-31.

MRI Findings in Hypoglycemic Encephalopathy

Kang et al describe the DWI findings in 11 cases of hypoglycemic encephalopathy. They found symmetric, potentially reversible diffusion restriction in the centrum semiovale (82%), cortex (73%), corona radiata (64%), internal capsule (54%), and hippocampus (36%). The cortical involvement was limited to the frontal and parietal lobes in a non-vascular distribution. Unlike prior reports, they did not find lesions in the corpus callosu. None of the lesions enhanced.

These findings are nonspecific and may be seen in a variety of ischemic and metabolic disorders. Specifically, reversible diffusion restriction can also be seen in seizure, drug toxicity, viral encephalitis, and metabolic encephalopathy.

References

Kang EG, Jeon SJ, Choi SS, Song CJ, Yu IK. Diffusion MR imaging of hypoglycemic encephalopathy. AJNR Am J Neuroradiol. 2010 Mar;31(3):559-64.

Familial Mediterranean Fever

We had a patient with suspected familial Mediterranean fever down for a CT tonight. Luckily, Zissin et al had a nice review of the CT features of familial Mediterranean fever in the BJR.

Familial Mediterranean fever, also known as recurrent polyserositis, is an autosomal recessive condition that tends to occur in ethnic groups originating in the Mediterranean area: Sephardic Jews, Arabs, Turks and Armenians. Diagnosis requires genetic tests.

Patients typically present before the age of 20 with repeated, self-limited episodes of severe, diffuse abdominal pain and rigidity, and fever due to inflammation of serous (e.g., peritoneum) surfaces. Inflammation of synovial surfaces can also occur, leading to joint pain.

A minority of patients present with surgical emergencies (e.g., acute appendicitis or complicated small bowel obstruction). The remainder present with mild, non-surgical peritonitis characterized by nonspecific CT findings of mesenteric edema: Edematous and hyperemic peritoneal folds and greater omentum with vascular markings, interenteric exudates and fibrinonodular changes. Mesenteric lymphadenopathy and splenomegaly have also been reported.

Our patient ended up not having much of anything on CT.

References

Zissin R, Rathaus V, Gayer G, Shapiro-Feinberg M, Hertz M. CT findings in patients with familial Mediterranean fever during an acute abdominal attack. Br J Radiol. 2003 Jan;76(901):22-5.

Marine-Lenhart Syndrome

Marine-Lenhart syndrome, also known as nodular Graves disease, is the coincidence of Graves disease with TSH-sensitive functioning nodules. Thyroid scintigraphy shows the typical finding of diffusely increased activity with a decreased background, but with one or more cold nodules (suppressed by TSH).

References

Intenzo CM, dePapp AE, Jabbour S, Miller JL, Kim SM, Capuzzi DM. Scintigraphic manifestations of thyrotoxicosis. Radiographics. 2003 Jul-Aug;23(4):857-69.

Connatal Cyst

Connatal cysts, also known as coarctation of the lateral ventricles and frontal horn cysts, are cystic areas at or just below the superolateral angles of the body or frontal horns of the lateral ventricles anterior to the foramina of Monro. Unlike cystic lesions associated with periventricular leukomalacia, connatal cysts are thought to be due to approximation of the walls of the frontal horns of the lateral ventricles. They occur in less than 1% of low-birth-weight preterm infants and have been reported to resolve on follow-up imaging.

Differential considerations include:

• Subependymal cyst: Located below the superolateral angle of the body of the lateral ventricles posterior to the foramina of Monro.
• Periventricular leukomalacia: Located above the angle of the body or frontal horns of the lateral ventricles.

References

Epelman M, Daneman A, Blaser SI, Ortiz-Neira C, Konen O, Jarrín J, Navarro OM. Differential diagnosis of intracranial cystic lesions at head US: correlation with CT and MR imaging. Radiographics. 2006 Jan-Feb;26(1):173-96.

Tegmento-Vermian Angle

The tegmento-vermian angle is constructed on sagittal midline images of the fetal brain. It is the angle formed by lines along the anterior surface of the vermis and the dorsal surface of the brainstem. The angle should be close to zero. Large angles indicate elevation of the vermis due to the following:

• Developmental arrest of the vermis,
• Failure of fenestration of the fourth ventricle with subsequent elevation of the vermis, or
• Persistent Blake pouch cyst: The vermis will be normal.

References

Robinson AJ, Blaser S, Toi A, Chitayat D, Halliday W, Pantazi S, Gundogan M, Laughlin S, Ryan G. The fetal cerebellar vermis: assessment for abnormal development by ultrasonography and magnetic resonance imaging. Ultrasound Q. 2007 Sep;23(3):211-23.

Epidural Spinal Mass

Differential considerations for epidural masses include:

• Degenerative: Disc herniation, facet osteophytosis, ligamentum flavum hypertrophy, synovial cyst, ossification of the posterior longitudinal ligament
• Epidural lipomatosis: Prominent epidural fat. Seen with prolonged steroid administration or Cushing syndrome. Y-shaped configuration of thecal sac on axial images is characteristic.
• Fluid collections: Pseudomeningocele, hematoma, abscess, arachnoid cyst.
• Metastasis: The lesion shown here ended up being Ewing sarcoma.
• Lymphoma
• Nerve sheath tumors: Nodular, fusiform, or dumbbell-shaped mass associated with nerve roots.

Inflammatory Esophageal Pseudopolyp

The image shows a single filling defect in the distal esophagus that arises at the gastric cardia in a patient with known gastroesophageal reflux. This is the typical appearance of an inflammatory pseudopolyp, a thickened fold of gastric mucosa without malignant potential.

"Demonstration of a prominent straight gastric fold terminating in a smooth polypoid expansion near the squamocolumnar junction in a patient with reflux is characteristic of a benign inflammatory pseudopolyp, making endoscopy or biopsy unnecessary." If the appearance is not typical for a benign inflammatory pseudopolyp, the following may be considered:

• Adenomatous polyp: Arising from adenomatous tissue in the distal esophagus, usually within Barrett esophagus. Malignant degeneration is possible, especially in larger polyps, so endoscopic removal is recommended.
• Varices:
• Esophageal papilloma: Fibrovascular excrescences covered with squamous epithelium. No malignant potential, but usually removed endoscopically
• Leiomyomas:
• Foreign body: Food usually lodges above the esophagogastric junction. Glucagon can be administered to decrease pressure of the lower esophageal sphincter and allow passage of the bolus. More invasive measures can also be taken (e.g., endoscopic retrieval), Persistent impaction can lead to transmural ischemia and perforation. Once the bolus has passed or been removed, workup should be directed at excluding pathology (e.g., cancer) causing stricture.
• Cancer:

References

Styles RA, Gibb SP, Tarshis A, Silverman ML, Scholz FJ. Esophagogastric polyps: radiographic and endoscopic findings. Radiology. 1985 Feb;154(2):307-11.

Masticator Space Masses and Pseudomasses

The masticator space is divided into suprazygomatic and nasopharyngeal compartments by the zygomatic arch.

The nasopharyngeal compartment contains the ramus and posterior body of the mandible, the lingual and inferior alveolar branches of V3; the inferior alveolar artery and vein; and the muscles of mastication except the temporalis muscle. The suprazygomatic compartment contains the temporalis muscle.

The masticator space is separated from the parapharyngeal space by a fascial layer along the medial aspect of the medial pterygoid muscle that extends to the medial aspect of the foramen ovale.

Developmental lesions

• Capillary hemangioma: Presents in early infancy and demonstrates rapid growth with involution by adolescence. Look for phleboliths and intense enhancement on CT. Look for areas of signal void from associated high-flow vessels on MRI within proliferating capillary hemangiomas.
• Arteriovenous malformation: Look for areas of signal void on MRI from associated high-flow vessels.
• Lymphatic malformation: Usually fluid signal and attenuation, but may also have heterogeneous signal intensity and rapid enlargement from hemorrhage
• Epidermoid and dermoid cysts: Rare, but when they do occur, they tend to originate from the suprazygomatic compartment. Bony erosion on CT suggests dural involvement.

Inflammatory lesions

• Odontogenic abscess: The most common lesion of the masticator space. Uncontained infections may extend to the floor of the mouth, sublingual and submandibular spaces inferiorly and the suprazygomatic masticator space and skull base superiorly.
• Extension of sinus infection:
• Complication of parotid calculus disease:
• Osteomyelitis:
• Osteoradionecrosis: May mimic osteomyelitis. May be difficult to exclude coexistent tumor recurrence. Association of cortical defects distant from the position of original tumor should support osteoradionecrosis vs tumor recurrence.
• Inflammatory pseudotumor: Idiopathic. The fibrotic type demonstrates low T2-weighted signal and helps differentiate this lesion from malignancy.

Benign neoplasms

• Nerve sheath tumors: Most frequent benign tumors of the masticator space. Related to the V3 as it passes through the masticator space. May be extension of a well-circumscribed fusiform mass through the foramen ovale and adjacent middle cranial fossa. Usually intermediate on T1 and hyperintense on T2, but neurofibromas with a central fibrous core may have increased peripheral signal intensity and decreased central signal intensity on T2-weighted images.
• Meningioma:
• Osteoblastoma:
• Giant cell tumor:

Malignant neoplasms

• Chondrosarcoma: Arises from the temporomandibular joint
• Osteosarcoma:
• Local extension from the upper aerodigestive tract:
• Maxillary ameloblastoma: May extend posterolaterally into masticator space. Usually low grade, causing bony remodelling rather than destruction
• Perineural spread: Along trigeminal nerve. Look for smooth thickening and enhancement of the nerve, concentric expansion of the foramen ovale, obliteration of the Meckel cave and bulging of the cavernous sinus
• Metastatic disease:
• Rhabdomyosarcoma: Rare. Usually seen in childhood.
• Lymphoma:

Pseudolesions

• Masseteric hypertrophy: Enlargement of the masseter muscles. May obtain a history of tooth grinding. Bilateral in 50%. There is preservation of soft tissue planes, identical attenuation and signal to muscle, lack of pathological enhancement, associated pterygoid and temporalis muscle enlargement and hyperostosis at the site of masseteric attachment are useful in differentiating unilateral cases from more worrisome processes (e.g., lymphoma or leukemia).
• Denervation atrophy of the masticator muscles: Acute phase (<1 month): Increase in muscle size with high signal intensity on T2-weighted images and abnormal enhancement. Subacute phase (1–20 months): Abnormal high intensity on T1 and T2-weighted images and abnormal enhancement with moderate volume loss. Chronic phase (>20 months): Extensive fatty infiltration and volume loss without abnormal enhancement.Look for similarity of other muscles innervated by V3.
• Accessory parotid tissue: Lies superficial to the masseter muscle in ~20% of patients. Signal is identical to that of the parotid gland.

References

Connor SE, Davitt SM. Masticator space masses and pseudomasses. Clin Radiol. 2004 Mar;59(3):237-45.

Bladder Base Impressions in Women

The smooth bladder base impression characteristically seen in men with prostatic hyperplasia may also be seen in women. Differential considerations include several unrelated etiologies:

• Asymmetry of the pubic symphysis: Most common cause
• Cystocele
• Urethral diverticulum
• Levator ani impression
• Postoperative change
• Female urethral syndrome
• Vaginal fibromyoma
• Ectopic ureterocele
• Intramural bladder neoplasm

References

Pope TL Jr, Harrison RB, Clark RL, Cuttino JT Jr. Bladder base impressions in women: "female prostate". AJR Am J Roentgenol. 1981 Jun;136(6):1105-8.

Bladder Ears (Transitory Extraperitoneal Hernia of the Bladder)

A bladder ear, also called a transitory extraperitoneal bladder hernia, is a transient lateral protrusion of the bladder into the inguinal canal. This is seen in infants (up to 10%), where the urinary bladder is located in the abdomen, close to the internal inguinal ring. A bladder ear can also occur through the femoral ring.

Bladder ears are incidental findings during cystography or intravenous urography; however, up to 20% of infants have an associated inguinal hernia.

They may be mistaken for bladder diverticula; however, their smooth walls, and usually wide necks can help differentiate them from diverticula.

References

Allen RP and Condon VR. Transitory extraperitoneal hernia of the bladder in infants (bladder ears). Radiology. 1961 Dec;77:979-83.

Spinning-Top Urethra

Spinning top urethra refers to the appearance of a widened posterior urethra that is seen mainly in girls with urodynamic abnormalities. It is thought to be due to involuntary bladder contractions that are resisted by a voluntary increase in distal sphincter tension (to prevent urine leakage), resulting in distention of the posterior urethra.

The images, obtained in two different patients during voiding, show an irregular contour of the urinary bladder (more so on the bottom image), which is due to trabeculations. The widening of the posterior urethra gives us the spinning top urethra.

Vaginal reflux of contrast during voiding may mimic spinning top urethra on anteroposterior views, as contrast in the vagina is superimposed on the contrast-filled urethra. Look for the irregular walls of the vagina to steer clear of this confusion. Oblique views will also help by showing a contrast-filled vagina posterior to the urethra.

References

• Fernbach SK, Feinstein KA, Schmidt MB. Pediatric voiding cystourethrography: a pictorial guide. Radiographics. 2000 Jan-Feb;20(1):155-68;
• Saxton HM, Borzyskowski M, Mundy AR, Vivian GC. Spinning top urethra: not a normal variant. Radiology. 1988 Jul;168(1):147-50.

Urethral Diverticula in Women

Urethral diverticula are outpouchings from the urethra into the potential space between the urethra and vagina. Infection of Skene glands is thought to play a role in their pathogenesis.

They are seen in up to 40% of women (usually middle-aged) with chronic genitourinary conditions such as recurrent infections, postvoid dribbling, and dyspareunia. 60% may present concomitantly with urinary incontinence, typically due to drainage of the diverticulum causing postvoid dribbling, but stress incontinence can also be seen.

The most common finding is a painful mass in the anterior wall of the vagina that leads to the discharge of urine or purulent material after palpation. The classic clinical triad of dysuria, postvoid dribbling, and dyspareunia, like all such triads, is not common.

Tumors may develop within urethral diverticula, either benign or malignant. Adenocarcinoma is the most common (60% of cases), but transitional cell and squamous cell carcinoma can develop as well.

Voiding cystourethrography will show contrast filling the urethral diverticula if the necks are patent. Ultrasound (transvaginal, transperineal, endorectal, or endourethral) and MRI can also be used.

Differential considerations include:

• Anterior vaginal mass: Müllerian cyst, Gartner duct (typically occur in the anterolateral aspect of the proximal third of the vagina), vaginal epithelial inclusion cyst (commonly located in the lower posterior or lateral vaginal wall at sites of previous trauma), ectopic ureterocele (inserting into the vagina).
• Bartholin gland cyst: Typically located in the posterolateral introitus medial to the labia minora.
• Endometrioma of urethra:
• Urethral neoplasm: Squamous cell carcinoma.

References

• Chang YL, Lin AT, Chen KK. Presentation of female urethral diverticulum is usually not typical. Urol Int. 2008;80(1):41-5.
• Chou CP, Levenson RB, Elsayes KM, Lin YH, Fu TY, Chiu YS, Huang JS, Pan HB. Imaging of female urethral diverticulum: an update. Radiographics. 2008 Nov-Dec;28(7):1917-30.
• Hosseinzadeh K, Furlan A, Torabi M. Pre- and postoperative evaluation of urethral diverticulum. AJR Am J Roentgenol. 2008 Jan;190(1):165-72.

Anterior Intermeniscal Ligament on Radiographs

The anterior intermeniscal ligament of the knee (also called the transverse geniculate ligament or anterior transverse ligament) can be seen on radiographs as an opacity of soft-tissue density in the posterior part of the Hoffa fat pad.

The anterior intermeniscal ligament can be seen in about 60% of patients on MRI, and in about 10% of patients on lateral radiographs of the knee. On radiographs, the ligament is at least 3 mm thick and completely surrounded by fat.

References

• Aydingöz U, Kaya A, Atay OA, Oztürk MH, Doral MN. MR imaging of the anterior intermeniscal ligament: classification according to insertion sites. Eur Radiol. 2002 Apr;12(4):824-9.
• Sintzoff SA Jr, Stallenberg B, Gillard I, Gevenois PA, Matos C, Struyven J. Transverse geniculate ligament of the knee: appearance and frequency on plain radiographs. Br J Radiol. 1992 Sep;65(777):766-8.

Erdheim-Chester Disease

Erdheim-Chester disease, or non-Langerhan cell histiocytosis, is a disseminated xanthogranulomatous infiltration of unknown origin. Patients are typically in the 5th through 7th decades of life. The skeleton is most frequently affected, but up to 50% of patients have involvement of the lungs, central nervous system and retroperitoneum.

Erdheim-Chester disease predominantly involves the long tubular bones. The axial skeleton is less commonly affected.

On radiographs, there is symmetric diffuse or patchy medullary sclerosis or a coarsened trabecular pattern involving the diaphysis and metaphysis. The epiphysis is either spared or less severely affected. Cortical thickening can also be seen in the same distribution.

Bone or Gallium scintigraphy reveals symmetric bilateral uptake in the areas of radiographic abnormality.

MRI reveals replacement of normal marrow fat as low T1 signal and regions of low and high signal intensity on T2-weighted images. Contrast administration reveals heterogeneous enhancement with nonenhancing cystic components. We have also seen focal lesions with areas of internal fat.

The images above are from a 50-year-old man. The radiographs reveal symmetric patchy sclerosis in the long bones with cortical thickening in the distal femur. The bone scan reveals increased activity corresponding to the radiographic abnormalities.
May be considered in the differential diagnosis of fat-containing bone lesions.

References

Charest M, Haider EA, Rush C. An unusual cause of knee pain. Br J Radiol. 2007 Mar;80(951):227-9.

Landmarks on the Lateral view of the Proximal Tibia

Some simple rules for differentiating the lateral and tibial condyles, spines, and margins on a lateral view of the knee:

Posteriorly, the medial tibial condyle is larger and has a squared off appearance, while the lateral tibial condyle is slender.

The medial intercondylar tubercle arises more anteriorly, tends to have a single peak, and has a sharper posterior slope. The lateral intercondylar tubercle arises posterior to the origin of the medial intercondylar tubercle, can have two peaks, and drops off with a more gentle curve posteriorly

References

Jacobsen K. Landmarks of the knee joint of the lateral radiograph during rotation. Rofo 1976;125:399-404.

Watering Can Perineum

Watering can perineum refers to urination through the perineum due to multiple urethroperineal fistulas. Urethroperineal fistulas are most commonly caused by chronic inflammatory urethral strictures due to tuberculosis, schistosomiasis, or gonorrhea.

On retrograde urethrography, there is typically an anterior urethral stricture associated with multiple prostatocutaneous and urethrocutaneous fistulas.

It may be difficult to visualize the entire urethra, since instilled contrast leaks out of the fistulas before opacifying the more proximal urethra. Fistulography, therefore, may be needed to visualize the entire urethra.

Management includes treatment of the cause of stricture (e.g., antibiotics) and diversion of urine with suprapubic cystostomy. Once the fistulae have healed attention is directed to relieving the stricture.

References

Kawashima A, Sandler CM, Wasserman NF, LeRoy AJ, King BF Jr, Goldman SM. Imaging of urethral disease: a pictorial review. Radiographics. 2004 Oct;24 Suppl 1:S195-216.

Ureteral Pseudodiverticulosis

Ureteral pseudodiverticulosis refers to the presence of multiple small (< 4 mm in diameter) outpouchings along the ureters. There is bilateral involvement in about 70% of cases, and the upper and middle thirds of the ureters are involved in about 85% of cases. The pouches are made up of hyperplastic ureteral epithelium that partially protrude into the muscular layer of the ureter wall.

Ureteral pseudodiverticulosis is most commonly associated with chronic infection or inflammation, among other urinary tract pathologies, and occurs most commonly in older patients. There is an association with malignancy; therefore, close follow-up is recommended.

On urography, ureteral pseudodiverticulosis may appear as a few separate well-developed outpouchings or as closer, poorly developed ones.

Retrograde urography may allow better distension and visualization of pseudodiverticula. Post-drainage images may allow even better visualization due to stasis of contrast material in the pouches.

References

Wasserman NF, La Pointe S, Posalaky IP. Ureteral pseudodiverticulosis. Radiology. 1985 Jun;155(3):561-6.

Trabecular Bars of the Femur

Trabecular bars (also known as bone bars) are struts of normal trabecular bone crossing the marrow space at right angles to the long axis of the shaft. They are most commonly seen in the intertrochanteric region of the femur and the proximal tibial metadiaphyses.

They can give the appearance of a calcified chondroid matrix on frontal radiographs and are often misdiagnosed as representing an enchondroma.

The lateral radiograph of the femur is key. It reveals trabecular bars perpendicular to the long axis of the bone, seen en face on the frontal view. Trabecular bars are more apparent in patients with osteoporosis.

References

• Keats
• Manaster BJ. From the RSNA Refresher Courses. Radiological Society of North America. Adult chronic hip pain: radiographic evaluation. Radiographics. 2000 Oct;20 Spec No:S3-S25.
• Pitt MJ, Morgan SL, Lopez-Ben R, Steelman RE, Nunnally N, Burroughs L, Fineberg N. Association of the presence of bone bars on radiographs and low bone mineral density. Skeletal Radiol. 2011 Jul;40(7):905-11.

Solitary Lucent Epiphyseal Lesions in Children

The differential diagnosis for lucent lesions in the bone is extensive. We can narrow it down by age, location, and presence of other findings. Here we consider solitary lucent epiphyseal lesions in children.

• Brodie abscess:
• Langerhans cell histiocytosis: Well-defined lytic lesion without sclerotic rim, but can have an aggressive appearance.
• Chondroblastoma: Periosteal reaction can be seen in up to 30% of patients, but is never sunburst or Codman triangle.
• Enchondroma:
• Osteoid osteoma:
• Lymphoma:
• Metastasis:

References

Gardner DJ, Azouz EM. Solitary lucent epiphyseal lesions in children. Skeletal Radiol. 1988;17(7):497-504.