Teaching Case

Two patients were admitted because of a sudden onset of flank or abdominal pain. CT and MRI revealed a perirenal hematoma, which was caused by the rupture of the kidney due to a cystic renal cell carcinoma and a very rare Wilms´ tumor in an adult.

Case 1: A 62-year-old woman was admitted with an acute abdomen. Hemoglobin was decreased to 6,8 g/dl. MS-CT scan showed a large perirenal hemorrhage with compression of the left kidney. In the kidney itself a cystic tumor with calcifications was found (Fig. 1a, b) and a nephron-sparing nephrectomy performed. Macroscopically, the lesion looked like a hemorrhagic cyst. Unfortunately, histology revealed a cystic clear-cell renal-cell carcinoma (RCC) with regressive changes in a size of 6 x 5 x 1 cm. An MS-CT of the abdomen was already performed in 1993 and a tumor of the left kidney suspected, but then interpreted as a hemorrhagic cyst. Case 2: A 46-year-old man presented with a sudden onset of severe left flank pain without previous trauma. Initially hemoglobin was normal (16,0 g/dl), but dropped to 11, 6 g/dl within two hours. MS-CT showed a massive perirenal hematoma on the left side (Fig. 2a, b). Neither histology of a sample taken percutaneously nor an magnetic resonance imaging (MRI) examination of the kidneys could confirm or exclude a malignant tumor (Fig. 2c). After performing partial nephrectomy histological examination revealed a very rare nephroblastoma of an adult in a size of 3 x 2 x 1 cm. After recurrence of the nephroblastoma two months later, the patient was treated by neoadjuvant chemotherapy followed by radical nephrectomy.

To optimize management of patients with spontaneous perirenal hematoma it is important to diagnose the cause of bleeding preoperatively. McDougal et al. [1] were one of the first to review 78 cases of spontaneous perirenal hemorrhage. Most of the cases were due to renal tumors (57 %). 33 % of the tumors were malignant (predominantly RCC), whereas 24 % were benign (mostly angiomyolipomas (AML)). 18 % were caused by vascular diseases such as polyarteriitis nodosa. In the first reported case a cystic mass in the left kidney was found. To determine the management approach to cystic renal masses the Bosniak classification is used. Category I and II cysts are benign and do not need further evaluation, category IIF cysts are more complex lesions that do require follow-up, whereas category III and IV cystic masses should be surgically removed. The described tumor had attenuation values of 20 – 50 HU on unenhanced and enhanced CT, indicating a cystic lesion with hemorrhage. No enhancing soft tissue components could be identified. The mass contained thick irregular calcifications in its wall which play only a minor role in the evaluation of cystic renal masses [4]. Due to the hemorrhage exact evaluation of the lesion according to the criteria established by Bosniak was not possible, but it could be categorized as a IIF or III cystic mass. Contrary to the impression during surgery histological examination revealed a cystic clear-cell RCC. 12 years earlier a cystic lesion in the left kidney had already been detected, but had been interpreted as a hemorrhagic cyst, which would not require follow-up. Therefore it is important to keep in mind that approximately 10 % of RCC manifest primarily as a cystic mass [5]. In the second case the cause of the perirenal hemorrhage was a Wilms´ tumor in an adult. Whereas it is the most frequent abdominal malignancy in children, only 3 % of Wilms` tumors are reported in adults [6, 7]. CT and MRI studies reveal an inhomogenous renal mass with cystic areas, which can rupture. Differentiation from an RCC is not possible by imaging alone [8]; in most cases a Wilms` tumor is definitely diagnosed by histology only. Remarkable in this patient was the fact that no renal mass could be identified by CT or MRI.Because Wilms` tumor is very rare in adults, standardized treatment had not been established for a long time. Improved survival rates also in adult patients were achieved by risk-adapted treatment depending on the tumor stage and it`s histology [9] and by using multimodal treatment according to pediatric protocols [7] established by the SIOP. In general, in Wilms` tumors in adults early nephrectomy is recommended. 2/3 of spontaneous renal hematoma are caused by renal tumors, which usually can be seen in CT or MRI studies. Nevertheless it is important to keep in mind that even small tumors can rupture, so that the absence of a detectable renal mass does not always exclude a renal tumor.