Thursday, March 29, 2018

False Perpetuations: Ovarian Torsion, Doppler Ultrasound, and CT


Ryan schwope ovarian torsion ax CT
ovarian torsoin US Ryan Schwope
Contrast-enhanced CT (top) and gray-scale US (bottom) in the same patient, both modalities demonstrating right ovarian torsion. Note the enlarged and heterogenous right ovary, peripheral follicles, and ascites

  • False Perpetuation: After a normal CT for lower abdominal or pelvic pain, an ultrasound with color Doppler is necessary to "rule out ovarian torsion"
  • Ovarian/adnexal torsion is caused by complete or partial rotation of the ovarian pedicle on its long axis. This results in lymphatic and venous congestion, inturn limiting arterial inflow
    • Torsion of both the ovary and fallopian tube occurs more often than that of either structure alone
    • Occurs more frequently on the right
  • Findings on Ultrasound
    • Enlarged ovary
    • Eccentric mass (usually a cyst) serving as a lead point
    • Round/'full' ovary with a central 'ground glass' appeaerance
    • Peripheral follicles
    • The presence of (or decrease in) arterial/venous flow predicts a better outcome
      • The absense of ovarian flow suggests necrosis
    • Even if there is ovarian flow on Doppler imaging, there can still be torsion
      • One study (J Ultrasound Med 2001; 20:1083-1089) evaulated the use of Doppler in pathologic proven cases of ovarian/adnexal torsion and found:
        • No arterial or venous flow in 40% of cases
        • No venous flow, decreased arterial flow in 7% cases
        • No arterial flow, decreased venous flow in 33% cases
        • Decreased arterial and venous flow in 13% cases
        • Normal arterial and venous flow in 7% cases
      • A meta-analysis (Eur J Pediatr Surg 2015; 25:82-86) looked at different modalities in diagnosing ovarian torsion in pediatric patients. Regarding morphologic and Doppler criteria on ultrasound for the diagnosis of ovarian torsion, this study found:
        • Morphologic features: 92% sensitive and 96% specific
          • Some of the morphologic features reviewed:
            • Enlarged heterogenous ovary (compared to contralateral normal ovary)
            • Ovarian volume 12x larger than contralateral volume, or 75 mL absolute ovarian volume
            • Ovarian diameter 2.3x larger than contralteral diameter
            • Multiple peripheral cortical follicles with transudative fluid
            • Whirlpool-sign
            • Cystic mass, particularly > 5cm in diameter
        • Doppler: 55% sensitive and 87% specific
  • Thus, the diagnosis of ovarian torsion is made or excluded based on grayscale appearance, not the Doppler findings
  • Regarding CT and ovarian torsion
    • One study (Abdom Imaging 2015; 40:3206-3213) retrospectively evaluated the utility of Doppler ultrasound in the assessment of ovarian torsion following a negative contrast-enhanced CT (the ultrasound and CT were performed within a 24 hour period) found:
      • Of the 48 cases with ovarian enlargement (defined as greater than 5 cm), 11 had torsion
      • Of the 235 cases without ovarian enlargment, 0 had torsion
      • Other CT findings assessed:
        • Presense of free fluid
        • Uterine deviation
        • Fallopian tube thickening
        • Smooth wall thickening of a cystic mass
        • Ovarian fat stranding
        • Twisted Pedicle
        • Abnormal ovarian enhancement
      • The most common ultrasound finding associated with ovarian torsion was ovarian enlargement (either due to the enlarged ovary itself or a mass functioning as a lead point)
      • A completely negative CT was never associated with a Doppler ultrasound suspicious for ovarian torsion (negative predictive value of 100%)
  • There is no utility in the addition of a Doppler Ultrasound (specifically for the evaluation of ovarian torsion) following a negative contrast-enhanced CT of the abdomen and pelvis
  • Ovarian size should be used as a dominant feature in the exclusion of ovarian torsion on both CT and US
*This blog was inspired by and based on a workshop given at the Society of Abdominal Radiology 2018 annual meeting by Dr. Maitray D. Patel of Mayo Clinic Arizona

Wednesday, March 7, 2018

Cowpers duct syringocele

Ryan Schwope

Ryan Schwope

Ryan Schwope
Axial contrast-enhanced CT (top), axial T2W MRI (middle), and sag T2W with fat-saturation MRI (bottom)
demonstrate an ovoid cystic structure associated with the midline posterior aspect of the bulbous urethra
  • The Cowper glands (bulbourethral glands) are paired pea-sized accessory exocrine glands analogous to the Bartholin glands in females
    • The main glands lie within the urogenital diaphragm
    • The ducts insert into the bulbous urethra  
    • Provide lubrication of the urethra and protection of the sperm
  • Obstruction of the ducts may result in formation of retention cysts, also referred to as syringoceles
    • May be congenital or acquired 
    • Most often asymptomatic although when large, may result in urinary obstruction and hematuria
  • Categorized as either open or closed 
    • Open cysts communicate with the lumen of the urethra and may mimic a urethral diverticulum or even an ectopic ureter
      • More likely to cause symptoms of postvoid dribbling, purulent discharge and hematuria
    • Closed or imperforate cysts become dilated due to duct obstruction resulting in cyst dilatation and extrinsic mass effect on the bulbar urethra
      • More likely to result in obstructive symptoms
  • Imaging typically detects a Cowper duct cyst as a unilocular cystic lesion at the posterior or posterolateral aspect of the posterior urethra 
    • Open cysts may be opacified during urethrography 
    • Closed cysts may appear as a smooth extrinsic filling defect on the ventral wall of the bulbous urethra 
    • MRI is useful to exclude solid neoplasms and to detect complications such as hemorrhage or infection
  • Symptomatic cases are treated surgically with cyst unroofing. Transperineal ligation of the Cowper gland ducts may be performed in refractory cases

References


Thursday, March 1, 2018

Persistent Sciatic Artery

Axial and coronal CT images with intravenous contrast demonstrate a left persistent sciatic artery (long arrows) coursing through the greater sciatic notch and deep to the gluteus maximus muscle. Note the asymmetrically diminutive left external iliac artery (short arrows)

  • A persistent sciatic artery (PSA) is a rare vascular anomaly in which the internal iliac artery courses through the greater sciatic notch and in to the thigh
    • During embryonic development, the sciatic artery usually involutes as the femoral artery develops
    • Recognition of an unusually enlarged internal iliac artery and a diminutive external iliac artery are some clues in diagnosing a PSA
    • The PSA course runs close to the sciatic nerve, and can run within the nerve sheath in some cases
    • Distally, the PSA runs deep to the gluteus maximus muscle, coursing along the adductor magnus muscle
  • Reported in up to 0.03-0.06% of the population and can be bilateral in 20% of cases
  • PSA is considered complete when it is the dominant blood supply to the popliteal artery and incomplete with the femoral artery is the dominant blood supply to the popliteal artery
  • 5 types have been described:
    • type 1 is a complete PSA with a normal femoral artery
    • type 2 is a complete PSA with a incompletely developed femoral artery
    • type 3 is a incomplete PSA (only the cephalic portion is present) and normal femoral artery
    • type 4 is a incomplete PSA (only the caudal portion is present) and normal femoral artery
    • type 5 is when the PSA arises from the median sacral artery
  • Majority (80%) become symptomatic at some point presenting with intermittent claudication, ischemia, pulsatile mass or neurologic symptoms
  • Susceptible to repetitive trauma from sitting and hip flexion/extension
    • Results in premature atherosclerosis and aneurysm formation
    • Aneurysm found in 48%, and stenosis and occlusion of the PSA in 7% and 9%, respectively
References:
  1. Mcquaid M, Gavant ML. Posttraumatic pseudoaneurysm of a persistent sciatic artery. AJR Am J Roentgenol. 1995;164 (6): 1514-5. 
  2. Pillet J, Albaret P, Toulemonde JL, Cronier P, Raimbeau G, Chevalier JM. Tronc arteriel ischiopoplite, persistance de l’artere axiale. Bull Assoc Anat 1980;64:109e22.
  3. Pillet J, Cronier P, Mercier Ph, Chevalier JM. The ischio popliteal arterial trunk: a report of two cases. Anat Clin 1982; 3:329e31. 
  4. Gauffre S, Lasjaunias P, Zerah M. Sciatic artery: a case, review of literature and attempt of systematization. Surg Radiol Anat 1994;16(1):105e9.
  5. Bower EB, Smullens SN, Parke WW. Clinical aspect of persis- tent sciatic artery: report of two cases and review of the literature. Surgery 1977;81(5):588e95.

Wednesday, January 31, 2018

Dilated Cisterna Chyli: A Potential Mimicker of Lymphadenopathy

  ryan schwope
ryan schwope
Axial (top) and coronal (bottom) contrast-enhanced CT images
demonstrate a retrocrural fluid-filled tubular structure with imperceptible walls
 (black arrows), the classic imaging features of a cisterna chyli
    Ryan Schwope
    Coronal T2-weighted MRI shows the tubular cystic structure of the cisterna chili
    and it's continuity with the thoracic duct (white arrow)
  • The cistern chyli is a dilated lymphatic sac ommonly located in the right retrocrural region, at the level of L1-L2, extending 5-7 cm in CC dimension. It classically receives draining lymph from two lumbar trunks and an intestinal trunk, and continues cephalad as the thoracic duct
  • Can enhance on delayed MRI >5 min
  • Has an average size of 7.4 mm in the AP dimension, although some authors consider it dilated when ≥6 mm
  • Dilatation can be secondary to lymphatic damage from prior gastroesophageal or retroperitoneal surgery, uncompensated cirrhosis, hypoalbuminemialymphangioleiomyomatosis, elevated central venous pressure, and biliary obstruction
  • Size changes can vary depending on phase of respiration, hydration, and lower thoracic duct peristalsis
  • Important to know of this entity because it can mimic retrocrural lymphadenopathy in the oncologic setting
  • Mulitplanar reformations and MRI can help demontrsate the tubular cystic nature of the cistern chyli and its continuity with the thoracic duct 

References 





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Gout of the extensor mechanism of the knee

MRI of gout of the extensor tendons of the knee, with nodules in the distal quadriceps and proximal patellar tendons. Lateral conventional radiograph does not show any calcifications.
Patient with leukemia (note abnormal marrow signal) who presented with acute knee pain and pre-patellar soft tissue swelling. Imaging shows gouty tophi involving the extensor tendons of the knee, with nodules in the distal quadriceps and proximal patellar tendons (yellow arrows). Lateral conventional radiograph does not show any calcifications. Patients with cancer are pre-disposed to gout due to hyperuricemia in the setting of high cell turnover or treatment-related tumor lysis.

Tophaceous masses of gout at the knee are most commonly located on the medial aspect of the infrapatellar fat pad and anterior joint recess (~90% of cases), at the lateral femoral condyle at the attachment site of the popliteus tendon (~80%), and the intercondylar fossae (~70%). Involvement of the extensor mechanism (distal quadirceps tendon and the patellar tendon) is less common, but characteristic.

Gouty tophi present as lobulated or amorphous masses. On MRI, they are isointense on T1-WI and heterogeneously intermediate-to-hypointense on T2-WI, with variable enhancement. Well-defined erosions of the patella can be seen with large tophi. Large erosions can mimick malignancy. Calcifications, when present can help narrow the differential diagnosis; however, as in the case above, they may not always be present.

Differential considerations include:
  • Post-traumatic or reactive enthesopathy, hydroxyapatite deposition: Will have calcifications.
  • Tenosynovial giant cell tumor: Can have low signal due to hemorrhage. No calcifications.
  • Amyloid deposition: Typically low signal. Can have calcifications.
  • Sarcoma: Gouty tophi can get very aggressive and erode into the patella, mimicking a soft tissue sarcoma.

References