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ESSENTIAL INFORMATION

Key Differential Diagnosis Issues
- CT is most accurate imaging modality for diagnosis of hernias and associated complications
- US can be helpful for determining reducibility of hernias, as well as diagnosis of hernias, which are transiently reducible - Offers advantage of scanning patient in upright position or with Valsalva maneuver to elicit hernia - Efficacy of US for hernias is debatable in literature, and CT should certainly be 1st-line modality in patients with acute presentation or concerns for hernia-related complications - US should be reserved for nonurgent presentation in outpatient setting
- Evaluate any hernia for presence of complications, including bowel involvement, obstruction, and ischemia - Different types of hernias are associated with very different risks of complications
- Descriptive terms used to describe abdominal wall hernias - Interparietal (i.e., interstitial) hernia: Hernia sac is located in fascial planes between abdominal wall muscles without entering subcutaneous soft tissues - Richter hernia: Entirety of bowel circumference does not herniate (just antimesenteric border of bowel)
Helpful Clues for Common Diagnoses
- Inguinal Hernia - Most common type of external hernia (~ 80%) with indirect hernias typically congenital (due to weakness of processus vaginalis), and direct hernias usually acquired due to abdominal wall weakness - Hernia seen in groin region anterior to horizontal plane of pubic tubercle - Do not result in compression of femoral vessels (unlike femoral hernia) - Direct hernias: Hernia sac arises anteromedial to inferior epigastric vessels - Indirect hernia: Hernia sac arises superomedial to inferior epigastric vessels - 5x more common than direct hernias - Complications more common with indirect hernias
- Femoral Hernia - Most commonly seen in older female patients (especially > 80 years) but much less common than inguinal hernias - Hernia extends into femoral canal medial to femoral vein and inferior to inferior epigastric vessels with frequent compression of femoral vein - Hernia sac located posterior and lateral to pubic tubercle - Very high risk of complications (incarceration, strangulation) and mortality compared to inguinal hernias
- Ventral Hernia - General term encompassing hernias extending through anterior and lateral abdominal wall - Can be acquired or congenital - Epigastric hernias occur at midline through linea alba above umbilicus, while hypogastric hernias occur at midline below umbilicus - Incisional hernias occur through any prior surgical incision site - Most often occur within a few months (usually first 4 months) of surgery but can occur at later time points as well - Parastomal hernias(considered type of incisional hernia) are quite common adjacent to ileostomy or colostomy - Parastomal hernias tend to slowly develop and enlarge over time and are very common with end-colostomies (48%) and end-ileostomies (28%) but much less common with loop ileostomies (6%) - Even if asymptomatic, most ventral hernias get larger over time with increasing risk of complications, making surgical treatment advisable
- Spigelian Hernia - Hernia extending through defect in aponeurosis of internal oblique and transverse abdominal muscles - Arise along lateral margin of rectus abdominis muscles, at level of arcuate line, inferior and lateral to umbilicus - Usually congenital in children and acquired in adults (prior surgery, obesity, pregnancies, etc. are risk factors) - High risk of strangulation and incarceration
- Lumbar Hernia - Hernia extends through defect in lumbar muscle or thoracolumbar fascia (usually below 12th rib and above iliac crest) - Can herniate through superior (Grynfeltt-Lesshaft) or inferior (petit) lumbar triangles - Most (80%) are acquired, usually due to surgical incisions (especially renal surgery) - Complications uncommon due to typically large neck, which makes incarceration/strangulation uncommon
- Umbilical Hernia - Hernia at midline extends through umbilical ring (usually upper 1/2 of umbilicus) - Can be congenital (diagnosed in infancy) or acquired (usually in middle age) - Congenital type 8x more common in Black patients but most resolve spontaneously by 4-6 years of age - Acquired hernias associated with obesity, multiparity, and ascites - Very common and usually small/asymptomatic, but larger or symptomatic hernias may require repair
- Subcutaneous Abdominal Wall Mass (Mimic) - Any subcutaneous or intramuscular mass may be superficially mistaken for hernia on clinical examination, although distinction should be obvious on imaging - Consider inguinal lymphadenopathy, abdominal wall tumors, cryptorchidism (especially in children), abscess, hydrocele, varicocele, or hematoma as entities that may be mistaken for hernia on physical examination
- Enterocutaneous Fistula (Mimic) - Gas- or contrast-filled tract from intraabdominal bowel loop into anterior abdominal wall may be confused for hernia - Bowel loops often tethered to anterior abdominal wall at site of fistula - Careful examination illustrates lack of true abdominal wall defect
Helpful Clues for Less Common Diagnoses
- Obturator Hernia - Rare type of hernia extending through obturator foramen into superolateral obturator canal - Usually involves loop of ileum but can involve any pelvic viscera - Typically seen in older female patients (especially older or multiparous females) secondary to either pelvic floor defect or pelvic floor laxity - High risk of complications (incarceration, strangulation) and mortality
- Traumatic Abdominal Wall Hernia - Hernia in anterior abdominal wall developing at site of focal trauma - Majority occur in lower abdomen with iliac crest region very common due to seat belt injuries - Most commonly seen in young children < 10 years due to bicycle injury (e.g., handlebar hernia) but can also be seen in adults after high-energy trauma (e.g., motor vehicle collisions)
- Sciatic Hernia - Very uncommon hernia involving herniation of bowel loop through greater sciatic foramen laterally into subgluteal region - Occurs most often in female patients, likely as result of piriformis muscle atrophy - Can result in symptoms of sciatica as result of compression of sciatic nerve
- Perineal Hernia - Uncommon hernia with hernia sac extending anteriorly through urogenital diaphragm (most common) or posteriorly between levator ani and coccygeus muscles - Usually diagnosed in older women (> 50 years of age) with history of prior surgery in deep pelvis/perineum, prior pregnancies, obesity, or ascites
- Spermatic Cord Lipoma or Liposarcoma (Mimic) - Uncommon fat-containing mass arising in spermatic cord, which can extend into scrotum inferiorly or inguinal canal/retroperitoneum superiorly - When extending into inguinal canal, can mimic inguinal hernia, but lesion typically appears expansile and mass-like - Liposarcomas will often demonstrate internal complexity (or even soft tissue component) depending on degree of dedifferentiation - Well-differentiated liposarcomas may appear largely fat attenuation and are more apt to be confused for inguinal hernia containing omental fat - Usually appear hyperechoic on US (particularly when well differentiated) with similar echogenicity to subcutaneous fat

References

Selected References

Images

Selected Images

Inguinal Hernia Axial CECT shows a large right inguinal hernia containing multiple loops of small bowel without evidence of obstruction. Inguinal hernias account for the vast majority of external hernias.

Inguinal Hernia Coronal NECT shows a classic right inguinal hernia containing loops of small bowel without evidence of obstruction.

Femoral Hernia Axial CECT shows a herniated bowel loop in the left groin. Note the close relationship of the hernia to the femoral vessels at the level of the symphysis pubis, characteristic of a femoral hernia.

Ventral Hernia Sagittal volume-rendered CECT shows a ventral hernia containing loops of small bowel . The small bowel proximal to the hernia sac is dilated , compatible with small bowel obstruction.

Ventral Hernia Axial CECT in a patient with a history of prior thoracic surgery shows a fat-containing ventral hernia arising in the upper abdomen. Ventral hernias occurring above the umbilicus, as in this case, are termed epigastric hernias.

Spigelian Hernia Axial CECT shows a left abdominal spigelian hernia with multiple dilated loops of small bowel , compatible with small bowel obstruction.

Lumbar Hernia Axial NECT shows a large lumbar hernia in the right flank containing a portion of the right kidney .

Lumbar Hernia Coronal CECT shows a large lumbar hernia containing colon , small bowel , as well as a portion of the right hepatic lobe . Lumbar hernias are often secondary to prior surgical incisions and are particularly common after renal surgeries.

Umbilical Hernia Sagittal CECT shows an umbilical hernia containing ascites in a patient with cirrhosis and portal hypertension.

Enterocutaneous Fistula (Mimic) Axial CECT shows an enterocutaneous fistula with enteric contrast directly extending from the small bowel into the anterior abdominal wall .

Obturator Hernia Axial CECT shows a loop of small bowel lying between the obturator externus and pectineus muscles, compatible with an obturator hernia.

Traumatic Abdominal Wall Hernia Axial CECT in a trauma patient shows disruption of the musculofascial plane near the insertion into the iliac crest and thoracolumbar fascia. Note the presence of adjacent subcutaneous hematoma. The spleen was also lacerated (not shown). These findings are compatible with a traumatic hernia.

Spermatic Cord Lipoma or Liposarcoma (Mimic) Axial T1 MR shows a large mass with fat signal extending through the inguinal canal into the left scrotum. This was found to be a spermatic cord liposarcoma at resection.

Spermatic Cord Lipoma or Liposarcoma (Mimic) Sagittal US in the same patient shows that the mass is very echogenic as a result of its fatty component, a fairly common appearance for these lesions, and extends down to just above the testicle .

Additional Images

Subcutaneous Abscess (Mimic) Axial CECT shows a loculated fluid collection in the subcutaneous tissue adjacent to the site of incisional hernia repair (abdominal wall abscess).

Soft Tissue Neoplasm (Mimic) Axial CECT shows a partly calcified mass in the abdominal wall adjacent to a descending colostomy (metastatic colonic carcinoma).

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