Spigelian hernia

Clinical History

4 years history of intermittent appearance of painful lump in the left iliac fossa. Clinical examination and investigations normal.

Imaging Findings

The patient complained of intermittent appearance of a hard painful lump in the left iliac fossa region since 4 years. Every time the symptoms lasted for about 15 mins and the pain and lump disappeared by lying in curled up position. Previous clinical examinations in the clinics did not reveal any evidence of lump, expansile cough impulse or palpable defect. She denied bowel or urinary problems. Herniogram and two ultrasound scans showed no abnormality so was the examination during laparoscopic sterilisation.
In view of the intermittent nature of the presentation an open appointment was arranged for her to have an ultrasound scan and she had one done within an hour of the onset. This showed a spigelian hernia on the left side with a loop of small bowel as the content and the clinical examination confirmed the palpable tender lump. She had an emergency exploration which confirmed the findings of ultrasound scan and the bowel loop was reduced back as it was healthy and defect repaired using PHS mesh.

Discussion

Spigelian hernias are a rare group of hernias representing only 2% of all ventral hernias. But its diagnostic importance is based on the fact that in patients presenting electively there had been a delay of about 2 years between the onset of symptoms and treatment with an increased rate of emergency presentation (20-25%). The reasons being lack of awareness of such a condition, rare reporting and the non specific symptoms and vague clinical signs resulting in only about 50% of these cases being diagnosed clinically. Therefore radiological investigations play an important role in making the preoperative diagnosis of spigelian hernia.
Spigelian hernias are ventral hernias occurring through the spigelian fascia along the Spieghel’s semilunar line and lie under the external oblique aponeurosis. The spigelian fascia is formed by the aponeurotic layers of the transversus abdominis and internal oblique muscles of the anterior abdominal wall and it joins the lateral border of the rectus sheath along the semilunar line. It commonly occurs at a level referred as ‘spigelian hernia belt’ which is a transverse band between the level of umbilicus and the line joining both anterior superior iliac spines. This is because the aponeurotic fibres are more vertical in this region and result in easy splitting by increased intra-abdominal pressure. Rarely they can occur above or below this level.
Spigelian hernia is more common in women and occurs around 50 years of age. The symptoms may vary from well-localised constant abdominal pain with or without palpable lump to vague inconstant ache. Clinically it is difficult to feel a definite lump or a hernial defect as they are typically inter-parietal. The predisposing factors include previous abdominal surgery, obesity, abdominal trauma and increased abdominal pressure due to chronic obstructive airway disease and urinary outflow obstruction. They often develop complications like incarceration due to delay in diagnosis. The differential diagnosis include sarcoma, lipoma, spontaneous haematoma of rectus sheath and are sometimes diagnosed as appendicitis or diverticulitis.
Ultrasound scan is the goldstandard investigation in the diagnosis of Spigelian hernia. The findings include demonstration of discontinuity of the deepest layer of peritoneum and preperitoneal fat in transverse scans, hernial orifice in spigelian fascia, hernial sac in interparietal plane which is more prominent on valsalva maneuver, sac contents like intestine or omentum and demonstration of reducibility of the hernial content by echoprobe compression. Specific signs of incarceration include free fluid in hernial sac, bowel wall thickness in hernia (>4mm) and fluid within herniated bowel loop. Other supportive findings include dilated bowel loops in abdomen, absence of blood flow and peristalsis within hernia. Intramural gas and free gas in abdomen/hernial sac indicate complicated hernia. Compared to herniography, ultrasound scan is well tolerated and can be done in emergency. The advantages against CT scan are low cost and the ability to demonstrate the variation in real time sac presentation in relation to the variation in position of the patient and the Valsalva maneuver.

Differential Diagnosis List

Final Diagnosis

Spigelian hernia

URL:	https://www.eurorad.org/case/2922
DOI:	10.1594/EURORAD/CASE.2922
ISSN:	1563-4086