Angiomyolipomas are the most common benign renal neoplasms and are comprised of varying proportions of adipose tissue, smooth muscle cells, and blood vessels. They are typically found incidentally in imaging studies but may present with symptoms such as flank pain, hematuria, or in rare cases, rupture leading to hemorrhagic shock [4].

Diagnosing AML and its complications, particularly rupture, requires a comprehensive approach involving clinical evaluation, laboratory investigations, and imaging modalities. Although CT scan is often considered the first imaging modality for the diagnosis of AML [5], it has some limitations due to overlapping features with other renal masses, radiation exposure, and contrast-related complications.

PoCUS is a valuable tool in the rapid assessment of patients with renal pathology. It offers real-time visualization without radiation exposure and can provide crucial information about the presence of masses, free fluid, or signs of rupture [6]. The scan should be performed with the patient lying supine. A low-frequency curvilinear array transducer should be selected with an abdominal or renal preset. The transducer should be placed longitudinally over the posterior axillary line at the level of the xiphisternum to identify the kidney. The transducer should be swept anteriorly and posteriorly to identify any free fluid. Then the operator should rotate the transducer 90 degrees and evaluate the kidney in the transverse view. Typical features of AML include a well-defined structure surrounded by renal parenchyma with variable echogenicity due to the presence of fat and other tissues such as blood vessels and smooth muscles [7] (Fig. 3, Supplementary file, Video 1). In this case, PoCUS revealed a hyperechoic heterogeneous mass arising from the upper part of the right kidney, along with surrounding hypoechogenicity suggestive of free fluid, indicative of hematoma secondary to rupture.

Exophytic mass arising from the upper pole of the right kidney (arrow) showing hypoechoic smooth muscle (arrowhead) surrounded by hyperechoic fat (star)

Limited evidence exists regarding the use of ultrasound for diagnosing ruptured AML in the ED. A study conducted by Sapadin et al. reported a case where the US detected a ruptured AML, resulting in hemorrhagic shock in a young girl [8]. Another study by T. Zhang et al. from the ED documented a case of spontaneous rupture of renal AML in a pregnant woman [9]. In our patient, the PoCUS rapidly identified the ruptured AML resulting in rapid referral to interventional radiology and urology for definitive management.