Ultrasonography of acute retroperitoneum

Abstract

The retroperitoneum is an important space in the human body that is often implicated in a range Epub ahead of print of acute medical conditions, some of which can be life-threatening. Ultrasonography may serve as a pivotal first-line imaging technique when assessing patients with suspected retroperitoneal abnormalities. Effective ultrasonography of the retroperitoneum requires a comprehensive grasp of its anatomy, adjacent structures, and potential pathologies. Being well-acquainted with the imaging characteristics of acute conditions can meaningfully assist in an accurate diagnosis and guide subsequent management. This review article summarizes and illustrates the acute conditions involving the retroperitoneum through the lens of ultrasound imaging.

Keywords: Acute disease; Emergencies; Retroperitoneum; Ultrasound.

Fig. 1.. A case of acute left flank pain due to left upper ureteral stone.

A. Coronal sonography of the left kidney shows left hydronephrosis (asterisk) due to echogenic stones identified in the left upper ureter (arrow) in (B).

Fig. 2.. A subject with patent ureters.

Transverse ultrasonography of the bladder using advanced dynamic flow shows an urine jet as a distinct stream of urine entering the bladder.

Fig. 3.. A case of acute pyelonephritis.

Ultrasonography of the kidney shows swelling of the left kidney with hypoechoic foci (arrows) and loss of cortico-medullary differentiation, consistent with acute pyelonephritis.

Fig. 4.. A patient presented with fever, flank pain and pyuria.

Ultrasonography shows swelling and hypoechoic lesion (arrow) in the upper pole of the kidney, consistent with acute pyelonephritis.

Fig. 5.. A case of renal abscess.

A. Ultrasonography of the right kidney shows a well-defined hypoechoic mass (white arrows) due to renal abscess. B. Contrast-enhanced computed tomography of the right kidney shows a well-defined hypodense mass with an enhanced wall (black arrows) due to renal abscess.

Fig. 6.. A case of pyonephrosis and pyoureter.

A. Ultrasonography of the right kidney shows dilated right upper collecting system with fluid-fluid layering (arrow) suggesting pyocalyx. B. Sagittal ultrasonography of the pelvis in another patient shows ureterocele and pyouretrer with internal echoes due to suppurative echogenic debris (arrows) in the obstructed urotract suggesting pyonephrosis and pyoureter.

Fig. 7.. A case of type I emphysematous pyelonephritis.

A. Ultrasonography of the left kidney shows complete obscuration of the left kidney by the curvilinear high echogenicity (arrows) due to gas. B. Computed tomography shows complete destruction of the left renal parenchymal with gas content (arrows).

Fig. 8.. A case of type II emphysematous pyelonephritis.

A. Radiography of the abdomen shows loculated and bubbly gas (arrows) in the right renal area. B. Computed tomography with a modified lung window level shows gas in collecting system (white arrows) as well as gas and fluid content in the right kidney (black arrowhead) and perirenal space (black arrow).

Fig. 9.. A case of type II emphysematous pyelonephritis.

A. Ultrasonography shows echogenic foci in the left renal calyx (black arrow) and perirenal space (white arrows) due to gas content. B. Post-enhanced computed tomography shows gas in the collecting systems (black arrows) and perirenal space (white arrows) with subtle fluid content.

Fig. 10.. A case of acute pancreatitis.

A. Coronal ultrasonography of left upper abdomen reveals anechoic fluid collection in the left anterior pararenal space (arrows). B. Contrastenhanced computed tomography of the same patient shows fluid collection (arrow) in the left anterior pararenal space due to acute pancreatitis.

Fig. 11.. A case of acute pancreatitis complicated with retroperitoneal abscess in the left anterior pararenal space.

A. Coronal sonography of the left retroperitoneum shows hypoechoic abscess in the left retroperitoneum (arrows) lateral to the psoas muscle. B. Contrast-enhanced computed tomography confirms abscesses in in the left anterior pararenal space (arrows).

Fig. 12.. A case of mycotic aneurysm of abdominal aorta in a diabetic patient with periumbilical pain.

A. Right coronal ultrasonography of the retroperitoneum shows a hypoechoic lesion (arrow) adjacent to the aortoiliac arteries. B. Axial image of contrast-enhanced computed tomography of the same patient reveals a mycotic aneurysm (arrow) proved by surgery and bacterial culture.

Fig. 13.. Mycotic aneurysm of the infrarenal aorta complicated with rupture.

A. Left coronal sonography of the retroperitoneum shows a round hypoechoic mass due to abdominal aortic aneurysm with wall interruption (arrow). The aneurysm is associated with surrounding soft tissue or hematoma. B. Axial view of contrast-enhanced computed tomography shows rupture of the mycotic aortic aneurysm with wall interruption (arrowhead) and retroperitoneal hematoma (arrows).

Fig. 14.. A case of pulsating abdominal mass.

Color Doppler ultrasonography shows a Yin-Yang sign in the aorta suggestive of abdominal aortic aneurysm.

Fig. 15.. Two different obese diabetics with mycotic aortic aneurysms which could not be delineated by ultrasonography.

A. Contrast-enhanced computed tomography of the abdomen shows indistinct outline of the abdominal aorta with surrounding soft tissue strands (arrow) suggesting either aortic leak or mycotic aortic aneurysm. B. Contrast-enhanced computed tomography shows indistinct outline of the abdominal aorta with gas collections (arrows) indicating mycotic aortic aneurysm. The gas could not be well shown by ultrasound.

Fig. 16.. A case of retroperitoneal abscess due to complicated diverticulitis of the descending colon.

A. Coronal ultrasonography of the left abdomen shows hypoechoic masses or fluid collections with internal echoes in the left retroperitoneum involving the left posterior pararenal space, psoas muscle (black arrows) and abdominal wall (white arrows). B. Contrastenhanced computed tomography shows abscesses with enhanced wall involving the left posterior pararenal space, left psoas muscle (black arrows) and left abdominal wall (white arrows).

Fig. 17.. A diabetic patient with gas-containing perirenal abscess presenting with right flank pain, fever and chills.

A. The lesion was not diagnosed by ultrasonography initially. B. Axial contrast-enhanced computed tomography performed one day after ultrasound shows right perirenal abscess with thick enhanced fascia (white arrows), gas contents (black arrows) and fluid collections that were not well detected by initial ultrasonography (A). P, abscess in the perirenal space; RK, right kidney.

Fig. 18.. A case of retroperitoneal abscess in the psoas muscle.

A. Right coronal ultrasonography shows multiple echogenic foci (arrows) in the right psoas muscle due to gas. B. Sequential axial view of contrast-enhanced computed tomography reveals a gas-containing abscess in the right psoas muscle (arrows).

Fig. 19.. A case of post-traumatic peri-renal hematoma.

Ultrasonography of the left kidney reveals post-traumatic laceration of the left renal parenchyma (black arrows) with hematoma at the perirenal area (white arrows).

Fig. 20.. A case of left renal hamartoma with spontaneous rupture presenting as acute left flank pain.

Ultrasonography of the left renal area shows a hyperechoic mass due to hamartoma (white arrow) with heterogenous lesion surrounding the left kidney due to hematoma (black arrows).

Fig. 21.. A case of acute left flank pain with hematuria due to emboli from the left cardiac atrium.

A. Contrast-enhanced computed tomography shows hypodense areas (arrows) in the left renal parenchyma which is consistent with renal infarct. The findings were not detected by ultrasound (not shown). B. Transcatheter left renal angiography displays filling defects (arrows) in the left main and segmental renal arteries.