History: Pregnancy was diagnosed via ultrasound with multiple live feti one month prior to presentation. Bitch never whelped and presented for evaluation. Large fluid-filled structure seen on ultrasound, no feti present. Patient is bright, alert and responsive on exam. Suspect hydrometra or pyometra following failed pregnancy. The patient was taken to surgery this morning for ovariohysterectomy. During abdominal surgery, observed an extremely large, fluid-filled structure closely adhered to and adjacent to the bladder neck, displacing all abdominal contents. Observed a normal left uterine horn and a dilated and enlarged right uterine horn. Closed abdomen for consultation with veterinary surgeon. Veterinary surgeon recommended an excretory urogram.
Images: Excretory urogram. Radiographs performed immediately following intravenous administration of contrast medium, 5 minutes, 20 minutes, and 40 minutes post contrast administration. Comparison radiographs are available for review, performed the day prior.
Findings: On the initial radiographs immediately following contrast medium administration, the left kidney is diffusely radiopaque with a small volume of contrast medium noted throughout the renal pelvis and proximal left ureter, which are normal in size, consistent with a normal nephrogram phase. The left kidney measures at the high end, but within the normal range for size, approximately 3.5 times length of L2. A normal right kidney is not visualized. There is a large soft tissue mass within the mid to caudal abdomen without evidence of opacification. There is loss of serosal margin detail and peritoneal gas, consistent with recent abdominal exploratory.
5 minutes following contrast medium ministration, there is persistent opacification of the left kidney, and progressive contrast medium is noted throughout the left renal recesses, pelvis and ureter. The left ureter is visualized extending caudally to the level of the ureteral papilla, and contrast medium is noted throughout the lumen of the urinary bladder and proximal urethra. The urinary bladder is markedly deviated towards the left aspect of the abdomen. Again, opacification of the soft tissue mass is not appreciated.
20 minutes following contrast medium administration, there is reduced opacification of the left renal cortex, persistent opacification of the renal recesses and pelvis, and progressive contrast medium accumulated within the urinary bladder. Questionably, there may be a faint soft tissue opaque rim of the large soft tissue mass on the lateral view.
40 minutes following contrast medium administration, there is persistent although mildly reduced opacification of the left renal cortex, recesses and pelvis. A mild volume of contrast medium is noted persistently throughout the left ureter, and the urinary bladder is progressively distended with contrast medium. There is a similar questionable faint soft tissue opaque rim of the large mass. A normal right kidney is not visualized.
A rounded region of soft tissue opacity is noted persistently within the right caudal thorax on the ventrodorsal projections. The caudal lungs appear unremarkable on the lateral views, therefore this is likely a superimposed opacity.
Conclusion: There is evidence of a normal left kidney and left ureter. There is no evidence of a normal right kidney, and therefore the large mid abdominal mass could represent an abnormal and non-functional right kidney, such as severe hydronephrosis, given the questionable faint soft tissue opaque rim seen on the images 20 and 40 minutes following contrast medium administration. However, the caudal location and deviation of the urinary bladder would be an atypical finding for a renal mass, therefore right renal agenesis could be possible, and the abdominal mass could represent a large ovarian cyst.
Recommendations: An abdominal ultrasound or a contrast enhanced CT of the abdomen could be performed to more thoroughly evaluate the large abdominal mass, to help determine the origin.
Follow-up: The patient was taken to surgery and the large mid-abdominal mass was removed. At surgery, there was no evidence of a right kidney. Histopathology of the large mass revealed a mesonephric duct cyst. The patient recovered uneventfully from surgery and is doing well post-operative.
Discussion: Mesonephric duct or Gartner cysts are congenital embryonic remnants resulting from the persistence of the male ductal system during sexual differentiation of the canine female genital tract. Both sexes have male (mesonephric) and female (paramesonephric) genital ducts. In females, the absence of testosterone causes failure of the mesonephric ducts to develop. Parovarian cysts can develop from mesothelium, mesonephric or paramesonephric remnants2. These cysts are found in a part of the broad ligament between the ovary and uterine tube2. They do not usually produce clinical signs unless they become large enough to cause abdominal distention, or other complications, such as rupture or torsion. In humans, paraovarian cysts constitute 10-20% of all ovarian tumor-like lesions in humans2. The occurrence in dogs is extremely rare2. There is a report of a 10 month old female toy poodle with a similar complex malformation of the urogenital tract, involving a Gartner duct cyst and ipsilateral renal agenesis, which has also been described in humans3.
1. Bartel, C. et al. Ectopic Endometrial Tissue in Mesonephric Duct Remnants in Bitches. Reproduction in Domestic Animals. Volume 46, Issue 6. March 2011.
2. Hyejin, K. et al. A Giant Parovarian Cyst in a Dog with a Granulosa Cell Tumor. JVMS. 2012. 74 (3): 385-389.
3. Fujita A, et al. Complex malformation of the urogenital tract in a female dog: Gartner duct cyst, ipsilateral renal agenesis, and ipsilateral hydrometra. JJVR. May 2016. 64 (2): 147-54.