Acute pyelonephritis and subcapsular hematoma revealing a nephroblastoma

Abstract

Nephroblastoma tumor is the most common renal tumor in children aged 1 to 5 years, typically presenting as an abdominal mass. However, other nonspecific signs may also reveal the disease. An unusual presentation, such as acute pyelonephritis or a subcapsular renal hematoma, is rarely an initial warning sign and should prompt investigation of an underlying cause, especially in the absence of trauma history. We report here a particular case of Wilms tumor, revealed by acute pyelonephritis and complicated by a subcapsular hematoma in a 6-year-old girl. We emphasize the importance of considering the diagnosis of Wilms tumor in any child presenting with renal hemorrhage, to improve prognosis and initiate therapeutic management as early as possible.

Keywords: Acute pyelonephritis; Imaging; Nephroblastoma tumor; Subcapsular renal hematoma.

Fig. 1

Longitudinal ultrasound of the left kidney showing a subcapsular collection (yellow star) at the upper pole, hypoechoic, corresponding to a subcapsular hematoma.

Fig. 2

Axial CT scan of the abdomen without contrast (A) showing a subcapsular collection in the left kidney (red arrow), spontaneously hyperdense: Subcapsular hematoma of the kidney. Contrast-enhanced abdominal CT in the same patient during the nephrographic phase, in axial slices (B and C), showing a well-encapsulated tissue mass in the lower pole of the left kidney, enhanced after contrast injection (yellow star), with evidence of diffuse acute nephritis foci (blue stars).

Fig. 3

Follow-up CT urography without contrast (A), and in the nephrographic phase, in axial (B) and coronal (C) views, demonstrating an increase in size of the left renal mass, measuring:95 × 87 mm. The mass remains well encapsulated, with heterogeneous density: both enhanced tissue and cystic areas, without calcification. It does not cross the midline or infiltrate neighboring organs. No vascular thrombosis or associated lymphadenopathy was observed.

Fig. 4

Axial MRI urography in T2-weighted FATSAT sequence (A), diffusion sequence with ADC mapping (B and C), and T1-weighted gradient echo after Gadolinium injection (D), showing the left renal lesion (yellow star), which is well encapsulated, with 2 components: cystic and tissue. It appears with intermediate T2 signal, diffusion restriction, and enhancement after Gadolinium injection.