Inguinal hernia

Etiology and role in the development of intestinal obstruction

An inguinal hernia belongs to the category of external hernias (hernias) and is one of the most frequent causes of acute mechanical small-bowel obstruction (Mechanical Small-Bowel Obstruction). Along with adhesions, neoplasms, and Crohn's disease, hernia incarceration leads to impaired passage of intestinal contents.

In the patient evaluation algorithm, the first and primary sign (Hallmark) is the detection of dilated bowel loops proximal to the obstruction and collapsed loops distal to it. A careful examination of the so-called transition point (Transition point) is absolutely necessary to establish the exact cause of the obstruction—whether it is an incarcerated inguinal hernia, mass, stricture, or intussusception.

CT diagnostics and identification of the "transition point"

Abdominal computed tomography (CT) plays a crucial role in acute obstruction triggered by a hernia. The method is indicated for high-grade obstruction, palpable masses, or signs of sepsis. CT allows precise determination of the level of incarceration and rules out other causes of an "acute abdomen".

The most reliable CT criterion is the presence of a "transition point". Identifying this zone is significantly facilitated by the small bowel feces sign (SB 'faeces sign'). It is characterized by the presence of feces-like material mixed with gas bubbles within the dilated loops proximal to the site of obstruction. This phenomenon occurs as a result of marked stasis and active water absorption by the intestinal wall.

Signs of strangulation and indications for surgery

The most formidable complication of an incarcerated inguinal hernia is closed-loop obstruction (Closed-loop obstruction). It is typically characterized by a U- or C-shaped configuration of dilated loops, their fixed radial distribution, and prominent, taut mesenteric vessels converging toward the twist point.

Targeted search for complications includes assessing bowel viability. The following signs of strangulation (Strangulation) indicate the development of ischemia, bowel infarction, and the risk of perforation:

• Bowel wall thickening with increased radiodensity.
• Poor or absent contrast enhancement of the bowel wall.
• Engorgement (engorgement) of mesenteric vessels.
• Mesenteric haziness (mesenteric haziness).
• Pneumatosis intestinalis (gas in the wall).
• Presence of air-fluid levels and stretched circular folds.

Important: The detection of ischemic changes in the incarcerated bowel wall or adjacent mesentery requires emergency laparotomy.

Specialized imaging techniques

If hernia incarceration causes only partial obstruction, standard CT with oral contrast may have limited diagnostic value. In such cases, CT enterography (CTE) and CT enteroclysis are used.

These methods combine the advantages of volumetric contrast enhancement and allow a detailed assessment of the degree of partial obstruction as well as extraintestinal manifestations, including vascular disorders. When partial obstruction is suspected, CT enterography demonstrates higher sensitivity (89% vs. 50%) and specificity (100% vs. 94%) compared to standard CT. Magnetic resonance imaging (MRI) is used as an alternative when radiation exposure must be avoided.

Differential diagnosis of acute scrotum

An incarcerated inguinal hernia may descend into the scrotum, causing sudden swelling and acute pain. Therefore, this condition must be differentiated from other inflammatory diseases of the scrotum (Inflammatory Diseases of the Scrotum).

Ultrasound is the imaging modality of choice. The differential diagnosis includes:

• Testicular torsion (Testicular Torsion): a surgical emergency. Ultrasound reveals ipsilateral increased echogenicity, absence of intratesticular blood flow, and the specific "whirlpool sign" when tracing vessels in the inguinal canal.
• Torsion of the testicular appendage (hydatid): characterized by a normal testis, an enlarged appendage, and the presence of fluid.
• Epididymitis (with or without orchitis): unlike torsion, it is accompanied by normal or increased color Doppler blood flow. Recurrent epididymitis in children requires ruling out urinary tract anomalies.
• Acute scrotal edema: sudden appearance of an edematous, hyperemic scrotal sac with completely normal ultrasound findings of the underlying structures.
• Acute hydrocele and post-traumatic sequelae.

Additionally, in the presence of a palpable scrotal mass, paratesticular rhabdomyosarcoma originating from the spermatic cord or epididymis should be ruled out; on ultrasound, it appears as a heterogeneous structure with increased blood flow.

Class and exam questions

What else to study on this topic

• Algorithm for evaluating small-bowel obstruction on CT
• Small bowel feces sign (SB 'faeces sign')
• Closed-loop (strangulated) obstruction: U- and C-shaped configuration
• Ultrasound signs of testicular torsion and the whirlpool sign
• Differential diagnosis of scrotal masses and inflammatory diseases

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.