Intraoperative ureteral injury with iatrogenic urinoma: multidetector CT-urography findings and role

Clinical History

A 66-year-old male patient was hospitalized to undergo elective colonic recanalization surgery. One year earlier, he had urgent resection of sigmoid and descending colon for diverticulitis with temporary colostomy, complicated by abdominal wall abscess.
Preoperative diagnostic workup diagnosed good performance status and normal biochemistry (including renal function).

Imaging Findings

Preoperatively, contrast-enhanced CT (Fig. 1) visualized normal appearance of left-sided colostomy excluding residual abscess collections in both abdomen and anterior abdominal wall. Double-contrast barium enema, performed through both rectum and colostomy, did not detect abnormal findings (Fig. 2). Left ureteral J-stent was positioned to minimize risk of intraoperative injury.
48 hours after elective surgical colonic recanalization, persistent abdominal pain and fever led to urgent request of CT (Fig. 3). With surgical drainage in place, a moderate-sized fluid-attenuation collection was detected in the peritoneal cul-de-sac.
After intravenous contrast administration, excretory phase acquisition completed with three-dimensional volume-rendering reformations detected opacification of the above-mentioned pelvic fluid collection from leaking distal right ureter, allowing diagnosis of iatrogenic urinoma.
Surgical correction including ureteral reimplantation was necessary.

Discussion

Although uncommon, iatrogenic urinary tract injuries (UTI) are well-known, potentially dangerous postoperative complications that may represent a source of concern due to the associated severe morbidity and occasional mortality. Increasingly diagnosed because of the large number and complexity of procedures, UTI may occur during gynaecological (two-thirds of cases), general surgical or urological procedures. Due to subtle and unspecific symptoms and signs, diagnosis is delayed in up to 80% of cases, with a median time to diagnosis of 6 days [1, 2].
Urinomas are defined as abnormal collections of extravasated urine resulting from disruption of the collecting system at any level, and most usually originate from the kidney. Alternatively, an urinoma may result from ureteral injury during gynaecologic, retroperitoneal pelvic or general surgeries such as colectomy for cancer, diverticulitis or inflammatory bowel diseases. Risk is further increased by prior abdominal surgeries and laparoscopy (compared to open laparotomy) [3, 4]. Prophylactic preoperative ureteral stent placement and surgical experience may be insufficient to prevent UTI occurrence and intraoperative identification [3, 5].
The lower ureter is most often (80-90% of cases) involved with lumen discontinuity, urine extravasation or both. Although minimally invasive endourological treatment with ureteral stenting is increasingly performed, treatment usually requires uretero-neocystostomy in the distal ureter, end-to-end anastomosis in the proximal and mid-ureter [2, 7]
Often clinically unsuspected, at multidetector CT (MDCT) urinomas usually appear as confined fluid-attenuation (0-20 Hounsfield Units, HU) collections on unenhanced scans, with opacification (up to 200 HU) corresponding to urine leak on excretory phase (5-20 minutes after injection). Opacification is inhomogeneous, denser close to the leaking source in larger lesions, and usually progresses over repeated delayed-phase acquisitions. Urinomas may have variable shapes, collect at different sites close to the laceration, or dissect into retroperitoneal compartments, resulting in diagnostic uncertainty and possible misinterpretation as ascites, abdomino-pelvic abscesses or hematomas, or cystic masses. Furthermore, multiplanar reformations and 3D volume imaging from MDCT-urography help in depiction of the UTI extent and ureteral stump [4, 6].
In conclusion, the diagnosis of urinoma from UTI should not be delayed or missed because of the associated significant morbidity. High clinical suspicion, awareness of its characteristic CT features and prompt appropriate imaging including multidetector CT-urography are crucial to avoid further complications such as abscess formation or hydronephrosis [1, 2].

Differential Diagnosis List

Final Diagnosis

Iatrogenic intraoperative ureteral injury with urinoma.

URL:	https://www.eurorad.org/case/10142
DOI:	10.1594/EURORAD/CASE.10142
ISSN:	1563-4086