Background

Traditional inflatable penile prosthesis (IPP) implantation has for decades involved reservoir placement into the space of Retzius (SOR). Using a penoscrotal approach to access the external inguinal ring, the transversalis is pierced. The reservoir is passed through this tunnel to reach its desired location deep in the pelvis (transinguinal [TI] technique). There the reservoir resides within the preperitoneal space, posterior to the transversalis fascia and anterior to the bladder (Figs. 1 and 2, A).

Despite the widespread practice of TI-SOR reservoir insertion over many decades, infrequent but severe reservoir-related complications are well recognized. Such complications include injury of the bladder at the time of reservoir insertion,¹ subsequent erosion of the reservoir into the urinary bladder,² neobladder,³ ileal conduit⁴ or colon,⁵ ureteral obstruction,⁶ small-bowel obstruction⁷ and compression of the external iliac vein leading to deep venous thrombosis.⁸ Distances from the external inguinal ring to the full bladder and to the iliac vein have been estimated to be only 2–3 cm.⁹ Bladder decompression, avoidance of dissection deep and lateral to the external ring, and use of Trendelenburg position at the time of reservoir insertion are recommended to minimize the risk of pelvic visceral injury during reservoir placement. The current era of robotic pelvic surgery has further elevated concerns for inadvertent intraperitoneal IPP reservoir placement among patients with altered pelvic anatomy.

Figure 1. Anatomical illustration of potential IPP reservoir positions. Intended location of HSM approach is indicated by Position 1.¹⁵

The introduction of the reservoir lock-out valve in the early 2000s facilitated alternative reservoir placement options without unwanted pressure-related auto-inflation of the cylinders. The “ectopic” reservoir concept was first popularized for penoscrotal IPP implantation by Wilson et al in 2002.¹⁰ In 2011, Perito popularized a similar ectopic approach during infrapubic IPP insertion with reservoir placement posterior to the anterior abdominal wall musculature and anterior to the transversalis fascia.¹¹ In Perito’s technique, the surgeon enters the external inguinal ring via an infrapubic incision and drives a nasal speculum cephalad and lateral toward the ipsilateral shoulder to bluntly develop a pocket posterior to the transversus abdominis.

In 2013, we coined the term “high submuscular” (HSM) reservoir placement, which differed from Perito’s approach by 1) utilizing a penoscrotal incision, 2) implementing a long atraumatic clamp to dissect a space above the pelvis and 3) emphasizing a more medial reservoir position posterior to the rectus abdominis (Fig. 1, Position 1).¹² Both approaches incorporate a TI approach with intent to remain anterior to the transversalis fascia in order to maximize the distance from the reservoir to critical pelvic structures such as the bladder and iliac vessels. High patient satisfaction and low rates of reservoir palpability supported the use of the HSM technique.¹² In 2015 Coloplast gained U.S. Food and Drug Administration approval for HSM IPP reservoir placement.¹³

Development of HSM Technique

Figure 2. Radiological examples of SOR (A) and HSM (B) reservoir placement. Reservoir is shaded blue, bladder/bowel yellow and external iliac vessels red.

Several critical appraisals of HSM reservoir placement merit discussion. Mayo Clinic researchers performed TI-HSM reservoir insertion on 20 cadavers followed by abdominopelvic exploration to determine the exact position of each reservoir.¹⁴ While 80% of reservoirs were anterior to the transversalis fascia, 20% were in unintended locations (10% retroperitoneal, 5% preperitoneal, 5% intraperitoneal). The authors highlighted the natural variability of inguinal canal makeup (ie fusion of abdominal wall layers) as a possible explanation for why blunt development of the HSM space may entail variability in final reservoir position.

At UT Southwestern, we recently conducted a decade-long retrospective analysis of reservoir location using cross-sectional radiographic imaging performed for nondevice-related reasons in the years following IPP insertion.¹⁵ Among 561 first-time IPP patients, 114 had imaging available for review by radiologists blinded to the method of reservoir insertion. Three different reservoir insertion techniques were used (29 TI-SOR, 80 TI-HSM, 5 counter-incision [CI]-HSM). Although substantial variability in the final resting positions of reservoirs placed with a TI-HSM approach was observed, reservoir-related complications in the TI-HSM group (total 405) were limited to 1 delayed bowel injury and 9 reservoir herniations. There were no complications in the CI-HSM group (total 25). Using the same radiographic database, the distances between reservoirs and critical pelvic structures were found to be roughly 5 times longer for HSM compared to SOR reservoirs.¹⁶ Major and minor mass effects from the reservoir onto the bladder or iliac vessels were significantly less common with the HSM approach (Fig. 2).

The HSM method of reservoir placement has become common practice among implanters worldwide, especially for higher risk patients like those with a history of colostomy, neobladder, hernia repair, renal transplant or other major pelvic surgery.¹⁷ In the only single-institution head-to-head comparison, patient satisfaction was higher among patients who underwent HSM than SOR reservoir placement.¹⁷ In 2020, a refined “Five Step Technique” for HSM reservoir placement was promoted to increase reproducibility and minimizing complications.¹⁸

We now regularly use a lower abdominal CI to avoid the location variability associated with TI insertion.^14,15 The CI-HSM approach allows for direct visualization of the transversalis fascia through the fibers of the rectus abdominis, avoids the need for manipulation of the inguinal canal and virtually eliminates the main risk of TI-HSM placement–reservoir herniation. The largest study to compare the CI-HSM technique (51) to non-CI techniques (483) found similar rates of device infection (2% vs 4%, p = 0.71) and an increased median operative time of 17 minutes with CI use.¹⁹

Summary

After a decade of clinical experience and refinement, the HSM approach for IPP reservoir placement has proven to be safe and well tolerated. Avoiding deep pelvic dissection in urological prosthetic surgery has become a popular strategy, especially in high-risk reoperative patients or when performed in an ambulatory surgical setting.

Disclosures: Dr. Morey receives honoraria for being a guest lecturer/meeting participant for Boston Scientific and Coloplast Corp. Dr. Dropkin receives honoraria for being a guest lecturer/meeting participant for Boston Scientific.