No 'safe zone' for low transverse incisions: ilioinguinal and iliohypogastric nerves.
Dr. Whiteside, a fellow in urogynecology at the Cleveland Clinic, said ilioinguinalal and iliohypogastric nerve injury is the second most common source of post-operative neuropathy following major pelvic surgery. The most common source of neuropathy is obturator injury (Obstet. Gynecol. 100:240-44, 2002).
"Injury to these nerves is usually heralded by intense burning pain in the lower abdomen, upper medial thigh, and pelvic region, with altered skin sensations in these same areas. The pain typically intensifies with increased intra-abdominal pressure--coughing, sneezing, or Valsalva," he said at the annual meeting of the Society of Gynecologic Surgeons.
Neuropathic pain is poorly relieved by narcotics, although slight hip flexion may temporarily relieve pressure on the nerves, he noted.
To determine whether precise incision and trocar placement could avoid these nerves, Dr. Whiteside and associates dissected 11 fresh frozen cadavers placed in a dorsal supine position to expose the plane between the external and internal oblique muscles.
The investigators located the entrance and termination points of 13 iliohypogastric and 16 ilioinguinal nerves, devising nerve maps to show their course in individuals and the group as a whole.
"We found considerable variability," said. Dr. Whiteside.
On average, the proximal end of the ilioinguinal nerve entered the abdominal wall 3.1 cm medial and 3.7 cm inferior to the anterior superior iliac spine (ASIS), but the locations ranged from 1.5 cm to 6.3 cm medial and -0.5 cm to 5.9 cm inferior to the ASIS, respectively.
Similar variability was seen in the termination points of the nerves, which averaged 2.7 cm lateral to the midline and 1.7 cm superior to the pubic symphysis.
The iliohypogastric nerve entered the abdominal wall an average of 2.1 cm medial and 0.9 inferior to the ASIS, following a linear course to terminate 3.7 cm lateral to the midline and 5.2 cm superior to the pubis symphysis, although striking variability also marked the course of this nerve in the specimens.
Because of this variability, "there does not appear to be a safe zone" for standard transverse lower abdominal incisions, and laparoscopic trocars placed in the right and left lower quadrants below the ASIS potentially may lead to postoperative neuropathy, Dr. Whiteside said.
On the other hand, trocars placed 2 cm above the transverse line connecting the right and left ASIS would appear to minimize injury to the iliohypogastric and ilioinguinal nerves.
Vertical incisions placed 1 cm on either side of the midline also appear to lie within a safe zone, he added.
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|Publication:||OB GYN News|
|Date:||Sep 1, 2003|
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