Diverticulitis Ultrasound: Common Signs and Effective Techniques

Ultrasound is an increasingly valuable tool for diagnosing diverticulitis, offering a noninvasive imaging option while avoiding radiation exposure from CT scans. Its real-time capabilities allow for dynamic assessment, aiding in evaluating disease severity.

Accurate interpretation requires proper scanning techniques and awareness of key sonographic findings. Understanding bowel wall layers and recognizing complications further enhance diagnostic confidence.

Scanning Technique Guidance

Optimizing ultrasound for diverticulitis evaluation begins with selecting the appropriate transducer and patient positioning. A high-frequency linear probe (7–12 MHz) provides superior resolution for assessing the bowel wall and surrounding structures. In patients with higher body mass index or deeper pathology, a lower-frequency curvilinear transducer (3–5 MHz) may be necessary for adequate penetration. The patient should be in a supine or left lateral decubitus position to improve visualization of the sigmoid colon, the most commonly affected site. Gentle probe compression displaces bowel gas, enhancing image clarity and allowing dynamic tenderness assessment to localize the inflamed segment.

Scanning should start in the left lower quadrant, where diverticulitis most often occurs, then extend to adjacent areas if needed. The graded compression technique helps differentiate inflamed bowel from surrounding structures by assessing compressibility and mobility. Inflamed segments are typically non-compressible and tender under probe pressure. Color Doppler imaging should be used to evaluate vascularity—hyperemia suggests active inflammation, while diminished flow may indicate complications like ischemia or perforation.

Diverticulitis is characterized by a hypoechoic, thickened bowel wall exceeding 4 mm, with echogenic fat stranding indicative of inflammation. Identifying an inflamed diverticulum as a hypoechoic outpouching with an echogenic center due to impacted fecal material supports the diagnosis. Free fluid or localized collections warrant further evaluation for abscess formation.

Key Ultrasound Signs Of Diverticulitis

Ultrasound findings primarily include bowel wall thickening, pericolic fat changes, and inflamed diverticula. Bowel wall thickening, typically exceeding 4 mm, is often asymmetric and localized to the affected colonic segment, most commonly the sigmoid colon. The wall appears hypoechoic due to edema and inflammation, with preserved stratification in milder cases. In advanced stages, the layers may become indistinct, suggesting extensive infiltration.

Surrounding fat stranding appears as hyperechoic, ill-defined areas adjacent to the inflamed bowel, representing inflamed mesenteric fat. The extent of echogenicity correlates with disease severity, with more pronounced fat changes indicating a more aggressive inflammatory process. Small pockets of free fluid near the affected bowel may signal perforation or abscess formation.

Inflamed diverticula appear as hypoechoic outpouchings with echogenic centers due to trapped fecaliths, strongly indicating acute diverticulitis. Hyperemia in the affected bowel segment, seen on color Doppler imaging, reinforces active inflammation. Increased vascularity suggests an ongoing inflammatory response, while absent blood flow may indicate ischemia or necrosis.

Interpreting Bowel Wall Layers

Ultrasound assessment of bowel wall layers provides insight into disease severity. The normal bowel wall consists of five alternating hyperechoic and hypoechoic layers, reflecting its histological structure. In early diverticulitis, the hypoechoic submucosal layer thickens due to edema and inflammation, disrupting the typical stratified appearance.

As inflammation progresses, the muscularis propria may hypertrophy in response to irritation. Normally hypoechoic and well-defined, it may appear disproportionately thickened. Loss of differentiation between the muscularis and adjacent layers suggests more extensive involvement, potentially indicating phlegmon formation. The outer serosal layer may become irregular, reflecting pericolic inflammatory changes.

Changes in echogenicity provide additional diagnostic clues. A hyperechoic mucosal layer may indicate early ischemic changes, while complete loss of stratification suggests severe inflammation or necrosis. Microbubbles or reverberation artifacts within the wall may signal gas-forming infection, raising concerns for perforation. A systematic evaluation of each layer improves diagnostic accuracy.

Identifying Potential Complications

Complications can significantly impact management, making their ultrasound identification crucial. Abscess formation occurs when localized infection leads to a walled-off pus collection. Sonographically, abscesses appear as hypoechoic or complex fluid collections with irregular margins, often containing internal debris or gas bubbles that create posterior acoustic shadowing. Gas within an abscess suggests bacterial activity.

Perforation may present as extraluminal air or free fluid in the peritoneal cavity. While ultrasound is less sensitive than CT for detecting pneumoperitoneum, reverberation artifacts or ring-down effects in the pericolic fat can indicate free air. Bowel wall discontinuity and extensive fat stranding further suggest microperforation. If perforation leads to peritonitis, surrounding inflammation may cause diffuse echogenic fluid collections or thickened peritoneal lining.

Fistula formation, though less common, can occur when chronic inflammation creates abnormal connections between the colon and adjacent organs. Ultrasound may reveal a hypoechoic, tubular tract extending from the bowel to structures like the bladder or small intestine. Air or fluid movement within the tract on real-time imaging strengthens suspicion of a fistula.

Differential Diagnoses

Several gastrointestinal conditions can mimic diverticulitis, requiring careful differentiation. Thickened bowel walls and pericolic fat changes can also be seen in inflammatory, infectious, or neoplastic processes. Clinical history and laboratory findings provide context, but ultrasound findings are key to diagnosis.

Acute appendicitis can resemble left-sided diverticulitis, particularly with a long or retrocecal appendix. The inflamed appendix appears as a non-compressible, tubular structure with surrounding fat stranding. Differentiation relies on identifying the blind-ended appendix with an obstructing appendicolith rather than a diverticulum.

Infectious colitis, such as Clostridioides difficile colitis, can cause diffuse bowel wall thickening with hyperemia on Doppler imaging. However, colitis typically affects a broader segment of the colon, whereas diverticulitis presents with localized thickening.

Colorectal carcinoma can also mimic diverticulitis, as malignancies cause focal bowel wall thickening and pericolic fat changes. Unlike diverticulitis, tumors often present as rigid, non-peristaltic segments with asymmetric thickening and irregular margins. Lymphadenopathy or intraluminal masses further raise suspicion for malignancy.

Ischemic colitis is another important consideration, typically displaying circumferential bowel wall thickening with decreased Doppler flow rather than the hyperemic response seen in diverticulitis. Recognizing these distinctions on ultrasound improves diagnostic accuracy and guides appropriate management.