A 51-year-old man presents to his primary care physician with complaints of fatigue and lethargy over the past few months. He also notes left flank and inguinal pain, which has become progressively more symptomatic over the past few weeks. He has no prior history of kidney stones or abdominal surgery.
Physical examination was remarkable only for mild left costovertebral angle tenderness. Routine laboratory testing revealed a creatinine level of 2.0 mg/dL, which was increased from his baseline of 1.1 mg/dL from the previous year. Results of a renal ultrasound demonstrated a normal-sized left kidney with moderate hydronephrosis and slight thinning of the parenchyma; his right kidney was normal appearing with no renal stones (Figure 1). Laboratory testing was repeated, and his creatinine level remained elevated at 1.7 mg/dL, with an estimated glomerular filtration rate (eGFR) of 43 mL/min/1.73 m2. Because of his compromised renal function, a computed tomography (CT) scan was obtained without intravenous contrast. The scan demonstrated moderate left hydronephrosis with slight thinning of the parenchyma and the suggestion of a lower pole-crossing vessel (Figure 2). Overall, the findings appeared to be consistent with a ureteropelvic junction (UPJ) obstruction. A MAG-3 (mercaptoacetyltriglycine) renal scan with furosemide demonstrated a compromised left renal function with delayed uptake, poor cortical transit, minimal excretion, and little response to furosemide. Left renal split function was reported to be 9%.
In most cases, a retrograde pyelogram at the time of pyeloplasty is not necessary. However, because this patient did not have cross-sectional imaging with contrast, a retrograde pyelogram was performed to obtain more information about the anatomy of the UPJ. The pyelogram showed obstruction at the UPJ and the suggestion of a crossing vessel; there was moderate hydronephrosis with blunted calyces (Figure 3).
Following the retrograde pyelogram, the patient was placed in a modified lateral decubitus position in preparation for robotic pyeloplasty. A four-arm technique is used in this procedure because the fourth arm can assist with retraction of the bowel and can be used to help elevate the UPJ after it has been dismembered. In patients with a left UPJ obstruction and a massively dilated renal pelvis, a transmesenteric approach can be considered. In this case, although there was moderate hydronephrosis, we used a standard approach, incising the white line of Toldt and medializing the colon to provide access to the ureter. After the ureter was identified, it was traced up toward the hilum, where we encountered two veins and one artery branch to the lower pole of the kidney, crossing anterior to the UPJ (Figure 4). These branches were dissected free, and we noted the UPJ and proximal ureter with a significant amount of filmy adhesive tissue, resulting in some kinking at the UPJ. The UPJ was transected anteriorly, which facilitated lateral spatulation of the ureter prior to completely dismembering the UPJ. The renal pelvis was then transposed anterior to the three lower pole vessels and anastomosed to the ureter using two 5-0 Vicryl™ (Ethicon, Somerville, NJ) sutures (Figure 5).
The patient had an uneventful postoperative course. At NYU Langone Health (New York, NY), we have an expedited postoperative care protocol for patients undergoing robotic renal surgery, such that the clear majority of patients can be discharged before 12 PM on postoperative day 1. The Foley catheter was removed in the morning and the patient ambulated and voided. There was minimal Jackson-Pratt (JP) output, and the patient’s JP creatinine level was consistent with his serum creatinine level, so the JP drain was removed, and the patient was discharged home. He returned 2 weeks later for cystoscopy and stent removal. He was doing well and had returned to regular, non-strenuous activities. Three months later, he reported no flank pain and improvement in his fatigue. The patient’s creatinine level improved to 1.3 mg/dL, with an eGFR of 58 mL/min/1.73 m2; a MAG3 renal scan showed an improvement in left renal split function to 32% (from 9%) with a post-furosemide half-life of 4 minutes. Six months postoperatively, the patient’s creatinine level was further improved to 1.19 mg/dL, with an eGFR of 64 mL/min/1.73 m2, and he remained asymptomatic.
UPJ obstruction can be due to intrinsic or extrinsic forces, and may be either congenital or acquired. The most commonly encountered cause of UPJ obstruction is a congenital abnormality due to an anterior crossing vessel to the lower pole, an aperistaltic segment of the ureter, ureteral kinking, or a high insertion.1 Symptoms of UPJ obstruction in an adult can be vague and mild or sudden and severe. In addition, a significant number of patients present with an incidental finding of hydronephrosis on an imaging study performed for unrelated symptoms.
The presence of hydronephrosis does not necessarily indicate ongoing high-grade obstruction, so additional testing is required to make the diagnosis. A renal ultrasound can assess the thickness and quality of the renal parenchyma and a Doppler resistive index >0.7 can be an indicator of obstruction. However, a cross-sectional contrast study is generally indicated to evaluate the relevant anatomy; a CT urogram is the study of choice because it can also evaluate for concurrent renal stones as well as assess for any crossing vessels. If stones have been ruled out by either an ultrasound and an abdominal radiograph or a prior noncontrast CT scan but clearer anatomical detail is still required, a magnetic resonance (MR) urogram is an excellent choice and is particularly beneficial in younger patients because it avoids radiation. In this case, a noncontrast CT scan was performed because of the patient’s renal insufficiency. MR imaging would have been a good follow-up, but the patient was unable to tolerate it.
Although CT and MR urography can also evaluate for obstruction and parenchymal thinning, the gold standard test for assessing obstruction and split renal function is a nuclear medicine renal scan. DMSA (dimercaptosuccinic acid), a cortical agent, is a better predictor of recovery after obstruction is relieved, whereas the tubular agents MAG3 and DTPA (diethylenetriamine pentaacetate) are better at assessing the degree of obstruction.
Indications for intervention include flank pain or nausea, which may be severe or chronic and nagging, pyelonephritis, concurrent kidney stones, or a decline in split renal function. This patient presented with only mild symptoms but with an elevated creatinine and evidence of significant left kidney dysfunction. Historically, split renal function <20% has been an indication for nephrectomy in symptomatic patients. However, this patient had what appeared to be a sudden rise in creatinine level over 1 year, and on ultrasound and CT scan, his renal parenchyma, although slightly thinned, appeared to be of reasonable thickness, which suggested that the renal scan may have underestimated the true amount of function. A recent study demonstrated the effect of laparoscopic pyeloplasty on 15 patients with split renal function <20%.2 The majority of these patients were symptomatic; median preoperative split function was 16.5% (range, 8.3%–19.6%) and improved to 23.7% (range, 14%–38%) at 12 months postoperatively, with resolution of flank pain and no recurrence in 93% of patients. Minimally invasive pyeloplasty has emerged as the gold standard for repair of UPJ obstruction, with less postoperative morbidity than open pyeloplasty and higher success rates than either open pyeloplasty or endopyelotomy.3,4
The patient elected to proceed with a robot-assisted pyeloplasty. If he had been asymptomatic, a reasonable alternative would have been to first place a ureteral stent and then assess for any improvement in renal function with serum creatinine and a repeat renal scan.