Indirect inguinal hernia
Indirect inguinal hernias are the most common type of abdominal hernias.
It is five times more common than a direct inguinal hernia, and is seven times more frequent in males, due to the persistence of the processus vaginalis during testicular descent.
In children, the vast majority of inguinal hernias are indirect.
Indirect inguinal hernias arise lateral and superior to the course of the inferior epigastric vessels, lateral to the Hesselbach triangle, and then protrude through the deep or internal inguinal ring into the inguinal canal. An indirect hernia enters the inguinal canal at the deep ring, lateral to the inferior epigastric vessels. It passes inferomedially to emerge via the superficial ring and, if large enough, extend into the scrotum.
- males: they enter the canal anterior to the spermatic cord and may extend through the external inguinal ring into the scrotum.
- females: they tend to follow the round ligament into the labia majora
Contents may include mesenteric fat (most common), small bowel loops, mobile colon segments (sigmoid, caecum, appendix).
Many are longstanding and asymptomatic, although the shear size can become burdensome.
Treatment and prognosis
- the most common complication associated with inguinal hernias, the incidence could be as high as 30% for infants younger than 2 months
- strangulation with bowel ischaemia and perforation
- intestinal obstruction
On imaging, consider:
direct inguinal hernia
- emerges medially to the to the inferior epigastric vessels and above the inguinal ligament
- inguinal canal is usually compressed/displaced ("lateral crescent sign")
- exit below the inguinal ligament and caudal to the emergence of the inferior epigastric vessels
On testicular ultrasound, one could consider spermatic cord lipoma on the differential if an inguinal hernia contains only omental fat. Movement of the fat with the Valsalva manoeuvre is more likely an indirect hernia.
- 1. Shadbolt CL, Heinze SB, Dietrich RB. Imaging of groin masses: inguinal anatomy and pathologic conditions revisited. Radiographics. 2001;21 Spec No : S261-71. Radiographics (full text) - Pubmed citation
- 2. Burkhardt JH, Arshanskiy Y, Munson JL et-al. Diagnosis of inguinal region hernias with axial CT: the lateral crescent sign and other key findings. Radiographics. 2011;31 (2): E1-12. Radiographics (full text) - doi:10.1148/rg.312105129 - Pubmed citation
- 3. Suzuki S, Furui S, Okinaga K et-al. Differentiation of femoral versus inguinal hernia: CT findings. AJR Am J Roentgenol. 2007;189 (2): W78-83. doi:10.2214/AJR.07.2085 - Pubmed citation
- 4. Hahn-Pedersen J, Lund L, Højhus JH et-al. Evaluation of direct and indirect inguinal hernia by computed tomography. Br J Surg. 1994;81 (4): 569-72. Pubmed citation
- 5. Cherian PT, Parnell AP. The diagnosis and classification of inguinal and femoral hernia on multisection spiral CT. Clin Radiol. 2008;63 (2): 184-92. doi:10.1016/j.crad.2007.07.018 - Pubmed citation