# Superior Hypogastric Plexus Block

## Introduction

The superior hypogastric plexus (SHP) block targets the sympathetic and visceral afferent plexus that transmits nociceptive signals from the pelvic viscera. First described by Plancarte et al. in 1990, this block is a valuable tool for managing pelvic cancer pain and select chronic pelvic pain syndromes that are visceral in nature. It provides targeted interruption of pelvic sympathetic and visceral afferent pathways without the somatic nerve blockade that accompanies epidural or intrathecal interventions.

## Anatomy

The superior hypogastric plexus is a retroperitoneal structure located at the level of the L5-S1 vertebral body junction (the sacral promontory). It represents the caudal continuation of the abdominal aortic plexus and is a bilateral network of nerves that merges in the midline anterior to the L5-S1 disc. The plexus lies in the retroperitoneal connective tissue between the bifurcation of the aorta (at L4) and the sacral promontory.

It receives sympathetic input from the lower thoracic and lumbar splanchnic nerves (T10-L2) and visceral afferent fibers from the pelvic organs. Inferiorly, the plexus divides into the right and left hypogastric nerves, which descend into the pelvis to join the inferior hypogastric (pelvic) plexus. The organs innervated include the uterus, cervix, vaginal fornix, bladder trigone, prostate, rectosigmoid junction, descending colon (distal to the splenic flexure), and the distal ureters. The plexus lies anterior to the L5-S1 disc and vertebral bodies, posterior to the sigmoid colon and mesenteric vessels, and medial to the common iliac vessels.

<image>Midsagittal anatomical illustration of the pelvis showing the superior hypogastric plexus draped over the anterior surface of the L5-S1 junction and sacral promontory. The plexus is shown as a network of nerve fibers converging from the aortic bifurcation above and dividing into the right and left hypogastric nerves descending along the pelvic sidewalls. Key anatomic landmarks labeled include: aortic bifurcation, common iliac arteries and veins, L5 vertebral body, sacral promontory, sigmoid colon, uterus (or prostate), bladder, and rectum. The retroperitoneal position of the plexus is emphasized.</image>

## Indications

### Pelvic Cancer Pain

Cervical cancer is the most well-studied indication, as pelvic pain from cervical malignancy is primarily transmitted through the SHP. Other cancer indications include endometrial, ovarian, and vaginal cancer with pelvic visceral pain; prostate and bladder cancer with deep pelvic pain; and rectal and sigmoid cancer pain (visceral component). The SHP block is most effective for visceral midline pelvic pain — somatic pain from pelvic sidewall invasion or sacral bone metastases requires alternative approaches.

### Chronic Pelvic Pain Syndromes

Non-malignant indications include chronic pelvic pain of presumed visceral origin refractory to pharmacologic management, endometriosis with deep pelvic visceral pain, interstitial cystitis/bladder pain syndrome (limited evidence), and radiation-induced pelvic pain. Results for non-malignant conditions are generally less consistent than for cancer pain.

## Fluoroscopic Technique

| Approach | Needle Path | Volume (Diagnostic) | Volume (Neurolytic) | Advantages | Risks |
|----------|------------|--------------------|--------------------|-----------|-------|
| Classic bilateral posterior | Lateral to L5 TP, anterolateral to L5-S1 | 8-10 mL/side (0.25% bupivacaine) | 6-8 mL/side (phenol or alcohol) | Standard approach; bilateral coverage | Iliac vessel puncture; limited by iliac crests |
| Transdiscal | Through L5-S1 disc, midline | 8-10 mL total | 6-8 mL total | Avoids iliac crests and vessels; single needle | Discitis risk (mitigated by antibiotics) |
| CT-guided anterior | Through anterior abdominal wall | Variable | Variable | Superior soft tissue visualization | Bowel/vessel injury |

### Classic Posterior Approach (Bilateral)

The patient is positioned prone on a fluoroscopy table. The fluoroscope is angled in an oblique view (approximately 15-30 degrees) to project the L5-S1 disc space and visualize the anterolateral border of L5. Bilateral 22-gauge, 15 cm needles are advanced under fluoroscopic guidance, passing lateral to the L5 transverse process and directed toward the anterolateral aspect of the L5-S1 junction. On the lateral view, the needle tips must be positioned at the anterior border of the L5-S1 disc/vertebral body, confirming retroperitoneal placement anterior to the vertebral column.

After negative aspiration, 3-5 mL of contrast is injected to confirm spread in a midline, craniocaudal pattern anterior to the sacral promontory. For a diagnostic block, 8-10 mL of 0.25% bupivacaine is injected per side. For a neurolytic block, 6-8 mL of 10% phenol or absolute alcohol per side is used after a confirmed local anesthetic response.

### Transdiscal Approach

A single midline needle is passed through the L5-S1 intervertebral disc to reach the anterior aspect of the disc. This avoids the iliac crest obstruction and iliac vessels that can make the classic bilateral approach challenging. The disadvantage is a risk of discitis, though this is low with antibiotic prophylaxis (intradiscal and IV). The transdiscal approach is particularly useful in patients with narrow bilateral access due to large iliac crests or bulky presacral tumors.

<image>Fluoroscopic illustration comparing the two main approaches for superior hypogastric plexus block. The left panel shows the classic bilateral posterior approach with two needles positioned lateral to the L5 vertebral body, tips resting at the anterolateral border of the L5-S1 junction on AP and lateral views, with contrast spread anterior to the sacral promontory. The right panel shows the transdiscal approach with a single needle traversing the L5-S1 disc in a midline trajectory, tip exiting anteriorly with contrast spread over the anterior disc surface. The iliac crests, common iliac vessels, and sacral promontory are labeled.</image>

## CT-Guided and Anterior Approaches

CT guidance provides superior soft tissue visualization and allows precise needle placement while avoiding vascular structures and viscera. It is particularly valuable when fluoroscopic landmarks are obscured by tumor distortion or prior surgery. An anterior CT-guided approach involves inserting the needle through the anterior abdominal wall, passing between bowel loops and vessels to reach the presacral space.

## Evidence Base

Plancarte et al. (1990) originally described the technique in 28 patients with pelvic cancer pain, with 70% reporting satisfactory pain relief and reduced opioid consumption. de Leon-Casasola et al. (1993) published a prospective study of 26 patients with pelvic cancer pain following neurolytic SHP block, with 72% achieving significant pain reduction. Gamal et al. (2006) compared neurolytic SHP block using phenol versus alcohol and found both agents provided significant pain relief at 3 months. Mishra et al. (2013) showed that SHP neurolysis reduced opioid requirements and improved quality of life in gynecologic cancer patients. The overall evidence supports a moderate level of recommendation for pelvic cancer pain, though fewer high-quality RCTs exist compared to celiac plexus neurolysis.

## Complications

Vascular puncture of the iliac artery or vein can cause retroperitoneal hemorrhage. Discitis is a risk primarily with the transdiscal approach, minimized with antibiotic prophylaxis. Transient leg weakness or paresthesia may occur from somatic nerve blockade if the needle is positioned too posterolaterally. Bladder or bowel dysfunction is transient and more common with neurolytic blocks due to parasympathetic fiber involvement. Intravascular injection into iliac vessels is avoided through aspiration and contrast confirmation. Infection is rare with proper sterile technique.

## Clinical Pearls

The SHP block is most effective for visceral pelvic pain that is midline or bilateral — lateralized somatic pain from pelvic sidewall invasion is better addressed by other approaches such as pudendal nerve block or an intrathecal pump. Needle tip position must always be confirmed on lateral fluoroscopy showing the tip at or anterior to the anterior vertebral body line, as a posterior position risks somatic nerve blockade. A diagnostic block with local anesthetic should always precede neurolysis, with a positive response (greater than 50% pain relief) predicting neurolytic success. The transdiscal approach is an excellent alternative when bilateral iliac crests obstruct the classic approach, but intradiscal antibiotics should always be used to reduce discitis risk. For comprehensive pelvic visceral denervation, the SHP block can be combined with a ganglion impar block when cancer pain extends to the perineum and coccygeal region.

## References

1. Plancarte R, Amescua C, Patt RB, Aldrete JA. Superior hypogastric plexus block for pelvic cancer pain. *Anesthesiology*. 1990;73(2):236-239.
2. de Leon-Casasola OA, Kent E, Lema MJ. Neurolytic superior hypogastric plexus block for chronic pelvic pain associated with cancer. *Pain*. 1993;54(2):145-151.
3. Gamal G, Helaly M, Labib YM. Superior hypogastric block: transdiscal versus classic posterior approach in pelvic cancer pain. *Clin J Pain*. 2006;22(6):544-547.
4. Mishra S, Bhatnagar S, Rana SP, et al. Efficacy of the anterior ultrasound-guided superior hypogastric plexus neurolysis in pelvic cancer pain in advanced gynecological cancer patients. *Pain Med*. 2013;14(6):837-842.