SRRP is clinically uncommon and can occur at any age, with a high prevalence in middle-aged and older adults above 45 years old[3]. Tas et al.[4] reported a case of SRRP in an 18-month-old child. SRRP is primarily caused by urinary stones, urinary tract infections, urinary cancer, rectal cancer, pregnancy, etc[5]. The same study also noted other etiological factors of SRRP, including ureteral stenosis, retroperitoneal fibrosis, spinal deformities, scar formation after radiotherapy, and vesicoureteral reflux[4]. One possible pathological mechanism of SRRP is that the mucosa of the renal pelvis becomes thin and brittle due to long-term obstruction and intrapelvic hypertension[6]. Exposure to external factors, including sneezing, coughing, and nausea can also induce an acute or intermittent increase in renal pelvis pressure, once the pressure reaches the critical value of 20–75 mmHg, the rupture of the renal pelvis and extravasation of urine occurs[7]. Studies have also reported the discharge of stones to the retroperitoneum[8]. The common crevasse is located in the fornix, i.e., the weakest part of the urinary collecting system[7]. Our case was considered to be ureteral obstruction due to cervical cancer compression because the diameter of the ureter traveling to the pelvis was already relatively smaller, and the ureter wall itself was thin and vulnerable to be compressed by pelvic masses. Moreover, in view of the pelvic MRI, cervical cancer had metastasized to distant organs, and even metastasis to other adjacent tissues in the pelvis and ureter could not be excluded, which resulted in ureteral stiffness and poor peristaltic ability. All of these contributed to the obstruction and occurrence of SRRP.
The clinical symptoms of SRRP are diverse, with renal colic being the most common feature which is considered to be caused by hypertension of the renal pelvis[9]. Secondly, SRRP may present as abdominal pain[10]. Abdominal pain can be renal colic radiating to the abdomen, and the inguinal region, penile, scrotum, and labia; it can also be chemical peritonitis caused by extravasated urine or infectious peritonitis caused by extravasated urine[11]. On physical examination, peritoneal irritation signs, and the presentation of peritonitis are often responsible for the delayed diagnosis and incorrect treatment[12]. Tuncay et al.[13] proposed that pain may not be an early manifestation; when urinary extravasation increases in size to form a urinary cyst, SRRP may present as a lumbar mass in the early stage, once the urinary cyst increases in size until it compresses the ureter or when extravasated urine becomes infected, lumbar pain symptoms will occur. Other symptoms of SRRP include nausea, vomiting, and gross hematuria[14]. As shown above, clinical manifestations of SRRP are diverse although without apparent specificity, causing misdiagnosis and delayed treatment. Thus, clinical manifestations of atypical abdominal pain or low back pain should signify the possibility of SRRP.
Diagnosis of SRRP primarily relies on imageological examination; ultrasound is the simplest and most convenient method for early detection of hydronephrosis and perirenal fluid[6]. However, its capacity for qualitative diagnosis of extravasated fluid is unsatisfactory; it cannot establish whether the fluid is urinary, hematogenous, or purulent[10]. Intravenous pyelogram (IVP) and CTU have prominent advantage in this regard, and are potential first choice tools for a definite diagnosis[15]. Based on the excretion of the contrast medium, it is possible to determine the nature of the extravasated fluid, the extent of urinary extravasation, and its etiology[6]. Especially, CTU can even reveal the crevasse because of its tomography principle[2]. As shown by CTU or IVP, we often detect contrast medium leaks into the renal sinus, the front area of psoas major muscle, and the retroperitoneum[5]. Koktener et al.[8] reported a case of contrast medium leaked into the abdominal cavity. However, special attention should be directed at the diuretic effect of the contrast medium, and increased pain during IVP or CTU examinations may be attributed to the diuretic effect of the contrast medium accelerating urine extravasation[16]. Yanaral et al.[17] classified SRRP into two degrees according to the extent of urinary extravasation, i.e., (1) grade 1 where urine is mainly obtained from the collecting system, and extravasated urine is only distributed in the lower kidney pole without a long-term fluid accumulation; (2) grade 2 where more urine is extravasated and spreads to perirenal, retroperitoneal, and periureteral areas. As is shown in this case by CTU, the contrast medium spread to the renal sinus, periureter, and front area of the psoas major muscle; this can be classified as grade 2. For differential diagnosis, right-sided SRRP should be distinguished from cholecystitis, hepatitis, appendicitis, pyelonephritis, and urinary stones[6]. On the other hand, left-sided SRRP should be distinguished from diverticulitis, pyelonephritis, and urinary stones[15].
The treatment of SRRP should first aim at controlling its etiology, i.e., treating the underlying cause of cervical cancer in this case[18]. The next step should be to reduce pressure in the renal pelvis[6]. For mild hydronephrosis with a small amount of urinary extravasation which has no tendency to spread, conservative treatments such as rest in bed, anti-inflammatory and antispasmodic treatment can be considered[10]. Literature search has revealed that double-J tube placement is the most commonly used method probably because stones are the most common cause of SRRP[1, 14, 19]. However, it must be noted that for ureteral obstruction caused by malignant tumors, we often encounter cases where the double-J tube cannot be placed successfully, and the effect of the placement of the double-J tube is limited[12]. If the double-J tube placement is failed or drainage is unsatisfactory, "ultrasound-guided percutaneous nephrostomy" may be considered[18]. In particular, percutaneous nephrostomy can be first considered for patients with severe urinary tract infections[20]. It is not only stronger than simple double-J tube placement in terms of drainage, but also has a greater advantage in promoting crevasse healing[18]. In addition, renal pelvic repair and nephrectomy are available depending on the case[19]. In our case, because the patient's low-back pain symptoms were not severe and the amount of urinary extravasation was not large, there was no indication for laparoscopic exploration. According to the current ureteral condition of the patient, unsatisfactory positioning of the Double-J tube may occur if the tube was placed for internal drainage to reduce pressure on the right collecting system. This would easily allow the double-J tube to pass through the crevasse, through cystoscopy. By subjecting a double-J tube to ureteroscopy, the increasing flushing pressure would easily enlarge the crevasse, aggravating extravasation risk. Thus, the patient was administered simple conservative treatment and recovered well based on the later follow-up.
In conclusion, in the treatment of SRRP, we should consider whether it is caused by stones first, and the presence of tumors including non-urinary tumors, especially pelvic tumors should not be ignored. Urography is the preferred diagnosis choice, treatment should be targeted at the etiology; double-J tube placement is the first choice of adjuvant therapy. Overall, the present findings have an important implications for improving patient prognosis.