Patient Selection

When superior hypogastric plexus block is used diagnostically in patients with chronic benign pelvic pain syndromes, it is designed to help define the source of the pain. It is used less frequently for this purpose than for neurolysis of the plexus to produce long-lasting pain relief in patients with pelvic cancers. Cancer pain syndromes that may be amenable to relief with a superior hypogastric plexus block include cervical, proximal vaginal, uterine, ovarian, testicular, prostatic, and rectal cancers. The technique has also been used to relieve pain in patients with distal colonic or rectal inflammatory bowel disease.

Pharmacologic Choice

During diagnostic blocks, the choice of local anesthetic should be determined by the desired duration of the block. Often, 0.25% bupivacaine or 0.2% ropivacaine with 1:200,000 epinephrine is used through bilaterally placed needles to a total dose of 20 to 30 mL. Shorter-acting local anesthetics such as 1% lidocaine, again often with 1:200,000 epinephrine, are also used effectively. When neurolysis is the goal, a radiocontrast agent, 2 to 4 mL through each needle, is used to ensure correct needle position; 8 to 10 mL of 10% aqueous phenol or 50% alcohol can be used as the neurolytic agent.

Anatomy

The superior hypogastric plexus is continuous with the intermesenteric plexus and is located retroperitoneally, caudad to the origin of the inferior mesenteric artery. It lies anterior to the lower part of the abdominal aorta, its bifurcation, and the middle sacral vessels; more specifically, it is anterior to the fourth and fifth lumbar vertebrae and the first sacral vertebra. The plexus is composed of a flattened band of intercommunicating nerve bundles that descend over the aortic bifurcation (Figs. 48-1 and 48-2). Broadening below, it divides into the right and left hypogastric nerves. In addition to its continuity with the intermesenteric plexus, the superior hypogastric plexus receives input from the lower two lumbar splanchnic nerves (Fig. 48-3). Figure 48-3 identifies with a red triangle a key concept in the superior hypogastric plexus nerve block. The red triangle highlights the anatomic window between the iliac crest, the L5 transverse process, and the L5-S1 vertebral bodies, which allows successful needle insertion.

Figure 48-1. Superior hypogastric plexus block: anteroposterior anatomy.

Figure 48-2. Superior hypogastric plexus block: cross-sectional anatomy.

Figure 48-3. Oblique anatomy of the superior hypogastric plexus. A, Anatomy. B, Concept of the red triangle for access to the superior hypogastric plexus.

In addition to sympathetic fibers, the superior hypogastric plexus usually also contains parasympathetic fibers that originate in the ventral roots of S2-S4 and travel as slender nervi erigentes (pelvic splanchnic nerves) through the inferior hypogastric plexus.

The left and right hypogastric nerves descend lateral to the sigmoid colon and rectosigmoid junction to reach the two inferior hypogastric plexuses. The inferior hypogastric plexus is a bilateral structure situated on each side of the rectum, the lower portion of the bladder, and the prostate and seminal vesicles (in the male) or the uterine cervix and vaginal fornices (in the female). Because of its location and configuration, the inferior hypogastric plexus does not lend itself to neurolysis.

Position

Patients undergoing superior hypogastric plexus block are placed prone on a radiographic imaging table with a pillow beneath the lower abdomen to reduce lumbar lordosis (see Fig. 48-2A). Ideally, biplane fluoroscopy is available to assess needle placement, for which oblique posteroanterior and lateral images are needed.

Needle Puncture

The L4-L5 interspace is identified fluoroscopically and skin marks are placed 5 to 7 cm lateral to the midline at the level of the L4-L5 interspace (Fig. 48-4). This preparation is needed for the insertion of the needles through the area of bony access (shown by the red triangle in Figs. 48-3 through 48-5) to the superior hypogastric plexus. After aseptic skin preparation, skin infiltration with local anesthetic is performed with a 30-gauge, 2-cm needle at the previously marked bilateral sites (Fig. 48-5). Local anesthetic infiltration is continued subcutaneously with a 22-gauge, 5- to 9-cm needle along the eventual caudomedial oblique needle path. The fluoroscopic beam is directed along the projected needle path to simplify needle insertion. The needle is then directed under fluoroscopic guidance to reach a point immediately anterior to the L5-S1 vertebral junction; the fluoroscopic beam is directed to minimize the needle hub’s radiographic size. If the fluoroscopic beam is directed properly, this approach should guide the needle tip to the correct position. The iliac crest and the L5 transverse process may obstruct passage of the needle; if this is the case, the needle is withdrawn and redirected in a cephalad or caudad angle to bypass the obstruction. As in the approach taken with either the celiac or lumbar sympathetic block, if the needle tip contacts the body of the vertebra (in this case, L5), the needle is simply redirected to “walk off” the body to its desired position immediately anterior to the L5-S1 junction (the sacral prominence).

Figure 48-4. Surface anatomy and skin markings important for superior hypogastric plexus block: posteroanterior view.

Figure 48-5. Technique for superior hypogastric plexus block using the red triangle to identify route of needle insertion and access to the superior hypogastric plexus. A, Anteroposterior view. B, Cross-section. C, Posterior oblique view.

Once the needle tip is positioned adequately and the position has been confirmed with biplanar fluoroscopy, the contralateral needle is inserted in a similar manner. Once both needles are positioned, radiocontrast medium (2 to 4 mL of Hypaque-M 60 [Sanofi Winthrop, Irving, Tex]) is injected to verify adequate placement. The radiocontrast agent should spread in a band immediately anterior to the sacral promontory; its smooth posterior margin should identify needle tip placement anterior to the psoas fascia. The contrast should spread toward the midline from the bilaterally placed paramedian sites.