Second 'pop-off' of fetal giant urinoma: case report and review

Abstract

Background: Renal fornices rupture with urinoma formation in fetuses is an unusual condition that acts as a 'pop off' mechanism to buffer renal pelvis pressure. Ureteropelvic junction obstruction (UPJO) is the most common cause of prenatal hydronephrosis, but it rarely leads to the formation of urinoma. Fetal urinoma could be indicative of poor renal function after birth. We report a rare case of UPJO-related urinoma accompanied with urinary ascites, which ruptured during vaginal delivery.

Case presentation: A 30-year-old woman was admitted to our hospital at 25⁺³ weeks gestation for fetal bilateral hydronephrosis. This probable case of UPJO became further complicated at 29⁺⁵ weeks with the presence of a urinoma around the left kidney and ascites. Afterwards, the urinoma gradually enlarged and the ascites worsened, accompanied by testicular hydrocele, pleural effusion, and polyhydramnios. The last prenatal ultrasound at 36⁺¹ weeks disclosed that the size of the urinoma was approximately 9.0 × 6.3x8.7 cm. The amniotic membrane ruptured prematurely and a male infant was vaginally delivered at 37 weeks. The baby developed gradually worsening abdominal distension. Bedside US revealed the urinoma became irregular and smaller, accompanied by a significant increase in ascites. It was speculated that the urinoma might experience a secondary rupture. Ascites drainage was performed and the urinoma disappeared. But it reemerged 2 days later with a significant increase in serum creatinine. The parents opted to abandon treatment. Surprisingly, the infant developed good feeding and mental health after discharge. Serum creatinine returned to normal at 3 months. Due to compression of surrounding tissues by the huge urinoma, the infant accepted urinoma resection surgery at 6 months. By the age of one, the infant was developing normally without signs of renal impairment.

Conclusions: Prenatal identification of a large urinoma with urinary ascites requires necessary attention and appropriate management strategies. Prenatal urinoma drainage is indicated for large urinoma risking dystocia or rupture during delivery. Postnatal ascites requires active drainage to prevent creatinine and urea reabsorption and other complications. Small asymptomatic urinoma can be managed conservatively, but early surgery is recommended for large or recurrent urinoma exerting pressure on surrounding tissues.

Keywords: Case report; Prenatal diagnosis; Renal fornices rupture; Ultrasonography; Urinoma.

Fig. 1

The formation of prenatal urinoma. A At 25⁺³ weeks gestation, US scan showed mild hydronephrosis in both kidneys, evident in the left kidney with pelvic dilation of 1.4 cm. B At 29⁺⁵ weeks, a urinoma (red Arrow) measuring 6.2 × 4.4x4.4 cm appeared around the left kidney, compressing renal parenchyma (blue Arrow) to one side. C At 31⁺⁶ weeks, MRI revealed further enlargement of the urinoma (7.3 × 6.3x6.8 cm). D At 36⁺¹ weeks, US disclosed ongoing enlargement of the urinoma (9.0 × 6.3x8.7 cm), along with bilateral testicular hydrocele (E) and ascites (green Arrow) (F)

Fig. 2

Postnatal changes in urinoma. A On the 1st day after birth, the urinoma became smaller and irregular, with noticeably decreased tension. B A discontinuity (purple Arrow) measuring approximately 0.15 cm was found in the lower parenchyma of the left kidney. C On the 2nd day, the urinoma disappeared after draining the ascites. D On the 4th day, the urinoma reemerged with a larger volume and multiple dense septations, pushing the renal parenchyma. E At one month after birth, US revealed that the urinoma persisted, with reduced separation, unclear cystic fluid, and hyperechoic protrusions on the cystic wall. F At 3 months of age, the size of the urinoma remained unchanged, with a smooth inner wall and clearer fluid

Fig. 3

CT urography at 6 months age revealed grade III hydronephrosis in the right kidney, a urinoma in the left kidney (A), and stenosis at bilateral renal pelvis ureteral junction (B, C)

Fig. 4

Pathological analysis revealed that the left renal mass exhibited cystic alterations, characterized by significant proliferation of fibrous tissue (green Arrow), chronic infiltration of inflammatory cells (blue Arrow), and formation of small blood vessels (red Arrow) within the cyst wall. Scale bar 100 µm

Fig. 5

The changes in serum creatinine levels and urinoma size, as well as the clinical management after birth