Renal cysts are a common incidental finding, with up to 40% of patients being diagnosed on renal tract imaging. Parapelvic cysts are more uncommon, representing only 5% of all renal cysts. They rarely cause obstruction and can be a diagnostic challenge, being commonly misinterpreted as hydronephrosis on ultrasound. Whilst endoscopic and percutaneous drainage are minimally invasive options, they pose a risk of recurrence. We present a case of surgical de-roofing of an obstructive parapelvic cyst with a robotic assisted approach as a more durable alternative.

A 76-year-old male was referred with decreasing renal function, with creatinine rising from 120 to 145 mmol/L. Renal tract ultrasound demonstrated a dilated left renal pelvis and CT urogram showed a parapelvic cyst measuring 62x59x55mm. Calyectasis observed on CT suggested compression from the cyst and functional obstruction. A DTPA study showed mild renal asymmetry with the obstructed left kidney contributing 42% of renal function compared 58% from the right kidney. It also noted reduced perfusion, cortical function and transit from the left kidney, consistent with a functionally significant outflow tract obstruction. The patient underwent a robotic assisted left renal cyst de-roofing. Dissection of the renal hilum revealed a large complex parapelvic renal cyst. As the ureter was traced up towards the kidney, a lower pole artery was seen compressing the cyst against the renal pelvis (Figure 1). The cyst was decompressed, and the cyst wall was excised. Following this, there was no longer compression of the lower pole vessel on the collecting system (Figure 2).

Post-operatively, the patient was discharged on day 3. His renal function returned to a baseline level of 120 mmol/L. Repeat DTPA demonstrated resolution of functionally significant obstruction with normal perfusion, cortical function and transit from the left kidney. A CT at 4 months demonstrated no recurrence, obstruction or hydronephrosis.

Parapelvic cysts are uncommon and even more rarely lead to obstruction. Diagnosis can therefore be challenging and often involves functional studies. Robotic assisted cyst de-roofing is a surgical option that provides durable results with a minimally invasive approach.