False Perpetuations: Ovarian Torsion, Doppler Ultrasound, and CT

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

Cowpers duct syringocele

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

1. Shebel HM, Farg HM, Kolokythas O, El-Diasty T. Cysts of the lower male genitourinary tract: embryologic and anatomic considerations and differential diagnosis. Radiographics. 2013 Jul-Aug;33(4):1125-43.
2. Surana S, Elshazly M, Allam A, Jayappa S, AlRefai D. A Case of Giant Cowper's Gland Syringocele in an Adult Male Patient. Case Rep Urol. 2015; 2015:682042.
3. Melquist J, Sharma V, Sciullo D, McCaffrey H, Khan SA. Current diagnosis and management of syringocele: a review. Int Braz J Urol. 2010 Jan-Feb;36(1):3-9.
4. Moskowitz PS, Newton NA, Lebowitz RL. Retention cysts of Cowper's duct. Radiology. 1976 Aug;120(2):377-80.
5. Kickuth R, Laufer U, Pannek J, Kirchner TH, Herbe E, Kirchner J. Cowper's syringocele: diagnosis based on MRI findings. Pediatr Radiol. 2002 Jan;32(1):56-8

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.