Management of Obturator Hernia

Abstract

The obturator hernia is a rare pelvic hernia that often presents with symptoms of bowel obstruction. Obturator hernia corresponds to 0.5–1.4% of all abdominal hernias. Entrapment of an intestinal segment within the obturator orifice, most often the ileum, less frequently Meckel’s diverticulum or omentum, can cause intestinal obstruction. The non-specific presenting symptoms make the diagnosis of this condition often unclear. Females are 6–9 times more likely than men to be subject to the pathology, mostly occurring in a multiparous, emaciated, elderly woman so it is also called “the little old lady’s hernia.” Risk factors such as chronic constipation, chronic obstructive pulmonary disease, ascites, kyphoscoliosis, and multiparty, can predispose patients to herniation. A sign of inconstant presentation may be the presence of a palpable mass or pain radiating from the inner thigh and knee—known as Howship–Romberg sign—but it could be misleading when confused with symptoms of gonarthrosis or lumbar vertebral disc pathology. CT scan of the abdomen and pelvis has been found to be the gold standard for preoperative diagnosis because of its superior sensitivity and accuracy with respect to other radiological exams. The only possible treatment for this pathology is surgery, and management depends on early diagnosis.

1. Introduction

1.1 Anatomy and embryogenesis

An obturator hernia (OH) is the protrusion of either an intraperitoneal or an extraperitoneal organ or tissue through the obturator canal [1]. The development of ossification of the ischium and pubis occurs between the 4th and 5th months of gestation, so perhaps it can be assumed that potential bone formation to fill the obturator foramen stops during this period. For anatomical purposes, the obturator foramen is a lacuna, and the obturator canal is the true foramen [2]. The obturator hole is an orifice located in the lower half of the iliac bone, below the acetabulum, limited by the pubis and the ischium (Figure 1). This orifice is almost completely blocked by the obturator membrane, a fibrous membrane in continuity with the periosteum of the margins of the foramen itself. This membrane consists of two layers and is covered by the internal and external obturator muscles that latch on it and the bone margin (Figure 2) [2].

Figure 1.

Endopelvic view of the obturatory canal. 1: superficial epigastric vessels; 2: anastomosis between epigastric and obturator vessels; 3: obturator foramen; 4: ileo-psoas muscle; 5: obturator nerve; 6: obturator vessels; 7: internal obturator muscle. with permission from Ref. [3].

Figure 2.

In vivo anatomy of the right obturator foramen. (with permission from Ref. [4]).

The obturator membrane does not cover the entire foramen: upwards it leaves a passage between its upper edge and the lower border of the horizontal branch of the pubis. This path is the obturator canal: an osteo-fibrous duct 2–3 cm long, directed obliquely from the inside out, which connects the pelvic cavity with the pre-obturator space of the thigh, between the external obturator muscle dorsally and muscles long adductor, comb, ileo-psoas ventrally. Its upper wall is the lower face of the horizontal branch of the pubis and as a floor, the obturator membrane, reinforced by an internal ligament. The canal is crossed by the obturator artery, vein and nerve. The obturator canal inwards is closed by the peritoneum, which may have a dimple at this level (obturator dimple) (Figure 1), enough to explain the possibility of obturator hernias, which occur in the upper part of the inner thigh region [5]. The canal offers a passage to the obturator peduncle, where the nerve is located above the artery and vein, and which contains a portion of adipose tissue. The obturator nerve, originating from L2, L3 and L4, divides into two branches at the emergence of the obturator canal. The ventral branch innervates the pectinate and the adductors muscles and supplies sensory branches to the medial face of the thigh; the dorsal branch also innervates the adductors and ends at the knee joint level. This anatomical arrangement explains the Howship–Romberg sign: in case of compression of the obturator nerve by a strangulated hernia, it occurs obturator neuralgia exacerbated by extension, abduction and internal rotation of the thigh, resolved by flexion [6].

The obturator artery originates from the internal iliac artery and it is divided into two branches, medial and lateral, forming a circle around the perimeter of the obturator foramen, in the thickness of its musculoaponeurotic operculum.

There is an anastomosis between the obturator artery and inferior or superficial epigastric artery which crosses the horizontal branch of the pubis. There may be an aberrant obturator artery that can originate from the superficial epigastric artery or the external iliac artery. These arteries are accompanied by satellite veins. This vascular circle has been called “corona mortis”, due to the high risk of bleeding. An anatomic variant has also been reported in which a pubic branch of the epigastric artery descending into the obturator foramen can replace the obturator artery, and a larger pubic vein draining into the iliac vein may replace the obturator vein.

2. Etiology

Arnaud de Ronsil in 1724 first described the obturator hernia, and then Henry Obre first successfully repaired it in 1851 [7].

Three anatomic stages in the formation of obturator hernia have been described. The first stage is the entrance of the pre-peritoneal fat tissue into the pelvic orifice of the obturator canal, forming a pilot fat plug. During the second stage, a peritoneal dimple develops through the canal and progresses to the formation of a peritoneal sac. The third stage consists of the onset of symptoms resulting from the herniation of the viscera into this sac [7, 8]. The formation of obturator hernia is favored by weight loss which involves the disappearance of the adipose tissue at the level of the obturator canal. This hernia is mainly formed in the elderly and thin women. In the beginning, the penetration of the extra-peritoneal tissue into the sub-pubic canal, then there is the formation of a dimple at the level of the peritoneum that covers it. Finally, a sac is formed with the risk of intestinal loops being inserted and their throttling due to the stiffness of the margins of the orifice. The sac can externalize directly through the exopelvic orifice of the canal, between the external obturator and pectineus muscles. However, it can also pass through the external obturator muscle or even fit between the two obturator muscles. The contents of the sac are usually the small intestine, more seldom an annex or ovary, bladder, appendix or epiploon. The narrowness of the orifice favors strangulation.

3. Clinical presentation

Obturator hernia is a rare pelvic hernia, accounting for the 0.5–1.4% of all hernias (Table 1) [9] that frequently causes bowel obstruction; the hernia passes through the obturator canal, bounded above by the obturator groove of the pubic bone, and below by the obturator membrane (Figures 3 and 4). The obturator canal is usually filled with fat and allows no space for hernia [3]. The fat disappears in patients who have had massive weight loss or are very thin indeed it is observed in elderly emaciated and multiparous women, so it’s also called “little old’s lady hernia” [10]. Right-sided OH is commoner than the left in the ratio of 2:1, as the left obturator foramen may be covered by the sigmoid colon [11], although an incidence of 6% bilateral hernias have been reported [12]. The hernia sac usually contains small bowel, rarely appendix, colon, Meckel diverticulum, or omentum [13]. A prompt diagnosis and treatment could avoid complications such as necrosis of the intestine that increases morbidity and mortality. Signs such as Howship–Romberg and Hannington–Kiff are aspecific and they should be associated with a CT-scan which is clearly the choice radiological exam. Symptoms such as the pain radiating from the inner parts of the thigh, the knee, or the hip could be confused with the dorso-lumbar intervertebral disc pathology or gonarthrosis [14, 15].

Hernia type	Percentage of presentation
Inguinal	75%
Incisional	10–15%
Femural	5–10%
Umbilical	—
Spigelian (at linea semilunaris)	—
Epigastric (linea alba)	—
Obturator	0.5–1.6%

Table 1.

The frequency of presentation in the general population of the types of abdominal wall hernia.

Figure 3.

Depiction of strangulated obturator hernia. (with permission from Ref. [3]).

Figure 4.

Intraoperative findings: the small intestine is incarcerated in the obturator foramen. (with the permission from Ref. [4].

Obturator hernia poses a diagnostic challenge and the signs and symptoms are often aspecific, which makes a preoperative diagnosis difficult. Obturator hernia should be included in the differential diagnosis of intestinal obstruction of unknown origin, especially in emaciated elderly women with chronic disease. The almost exclusive incidence of obturatory hernia in women can be explained by the greater extension of the obturator foramen and from the different obliquity of the pelvis that exposes it to a direct action of abdominal pressure in women. More frequent symptoms are due to an intestinal obstruction like abdominal pain, distension, nausea, vomiting and constipation [16]. They may also have recurrent attacks of intestinal obstruction in the past with or without a palpable mass in the groin. On physical examination, it may be evident the Howship–Romberg sign: in case of compression of the obturatory nerve by a strangulated hernia, it occurs an obturator neuralgia exacerbated by extension, abduction and internal rotation of the thigh, resolved by flexion. It is considered pathognomonic and presents in 15–50% of cases. The Hannington–Kiff sign (absent adductor reflex and an intact patellar reflex) is reported as more specific [17]. It would be necessary to perform a computed tomography (CT) to make a diagnosis. The CT has an accuracy of 90% [18]. An emergency exploratory laparotomy is fundamental in patients presenting with an acute abdomen.

4. Diagnosis

Abdominal plain radiograph shows aspecific signs of intestinal obstruction and very rarely may show a gas shadow in the area of obturator foramen, therefore, it is not an informative exam [19].

Herniography with the intraperitoneal injection of contrast material under local anesthesia was reported to be useful for demonstrating the hernial sac but it is not a reproducible examination in emergency conditions because it can be done only in elective cases [20].

Ultrasonography (US) is a noninvasive, cheap, and easily available diagnostic tool that can be used to diagnose OH accurately, especially in the emergency setup when patients present with the acute abdomen of uncertain cause, hence allowing early operative treatment. Using a high-frequency probe, the examiner could detect a hypoechoic mass corresponding to the dilated and edematous segment of the intestine posterior to the pectineus muscle [21]. The major advantages of US are that it is a non-invasive and allows for comparison with the asymptomatic side. Limiting factors are dependence on examiner experience (who may at times miss the diagnosis by not scanning the femoral region or may not recognize the hernia as it is small and found deep within the pelvic musculature) and the relatively long learning curve. Also, too much pressure on the transducer can reduce the sensitivity of detection of hernias [22].

Barium enema fluoroscopy can demonstrate a hank of intestinal loops but is very time-consuming and not feasible in cases of acute abdomen. Also, retained barium in the bowel loop may increase the risk of subsequent complications, hence it is not routinely advocated [23].

Magnetic resonance is a comparable method to CT scan for diagnosis but is not always available in urgency or in most cases of obturator hernia presentation [24].

CT scan (Figure 5) is more sensitive and specific, showing a mass-like lesion between the obturator externus and pectineus muscles (Figure 6), it is useful to shorten the lapse of time from presentation to appropriate diagnosis and spontaneously subjecting a patient to definitive surgery, and thus also giving a choice in the surgical approach required [14].

Figure 5.

CT scan, coronal: the arrow identifies the right obturator hernia sac; the small intestine is dilated. (with permission from Ref. [4].

Figure 6.

CT scan transverse section. (with permission from Ref. [4]).

5. Treatment

Once the diagnosis is obtained or in the diagnostic suspicion of obturator hernia, therapy is exclusively surgical: in the presence of signs of intestinal obstruction or incarceration, surgical exploration is mandatory. The manual reduction of an incarcerated obturator hernia has been described in cases of patients considered unfit for surgery, but two aspects must be considered: the early recurrence and the impossibility to explore the incarcerated viscera in case of possible evolution to gangrene or bowel infarction. If the incarcerated obturator hernia is not treated, it can be fatal and in any case, should always be repaired both in case of urgency and in case of non-acute symptomatology attributable to the hernia; it should be remembered that symptoms may persist and then result in incarceration. The current trend is to repair the obturatory foramen with the use of prostheses primarily made of polypropylene; however, if the orifice is less than 1 cm, the approach could also consist of direct repair. Currently, there is no consensus on the repair technique but it is all based on the surgeon’s experience and preference. The different feasible surgical approaches are intraabdominal, inguinal extraperitoneal, obturator or crural, Cheatle–Henry retropubic and laparoscopic approach [24, 25, 26, 27].

5.1 Intra-abdominal approach

In an emergency set-up usually, a midline incision by laparotomy is required to allow a wider exposure of the obturator ring, the pelvic floor and the lower abdomen, especially in the case of gangrenous bowel resection. Uncoiling the bowel discovers the dilated tract at the border with the strangulated one, usually with a lateral clamping: it is necessary to gently pull the bowel to reduce it in the abdomen avoiding rupture that would lead to septic contamination. The bowel is treated as in all cases of strangulation, preserving or resecting it depending on the degree of intestinal wall perfusion. Suturing the small orifice can be done with several techniques: simple direct closure with several stitches, two layers closure of peritoneum (Figure 7). For large defect: patching and plugging the canal with rib cartilage, peritoneal patch, periosteal patch, pectineal or adductor longus muscle flap with external oblique aponeurosis, greater omentum, round ligament, uterine fundus, ovary, urinary bladder wall, ox fascia, tantalum gauze, teflon cloth, marlex mesh, oxidized cellulose gauze (oxycel), polytetrafluoroethylene (PTFE), polypropylene mesh, Kugel patch, permacol patch plug [19] of mersilene, rolled up marlex mesh as a “cigar roll” plug and titanium alloy staples without mesh [24, 25, 26, 27, 28].

Figure 7.

Trocars placement in obturator hernia laparoscopic repair.

5.2 Laparoscopic approach

The laparoscopic approach, both–trans-abdominal pre-peritoneal (TAPP) or total extraperitoneal (TEP) [29], is feasible in expert settings: the position of the trocars, patient and operators is similar to that of the TAPP and TEP repair for inguinal hernia (Figure 8) [30, 31, 32]. Placement of a double-layer prosthesis is not recommended in the same manner as in abdominal wall hernias because the peripheral anchorage is not safe due to the presence of vascular and nerve structures. It is necessary to proceed as in TAPP repair for inguinal hernia: the peritoneum is dissected above the inguinal dimples, the dissection is conducted lower than the orifice of the obturator canal, the sac is reduced in the abdomen, and the prosthesis is placed in the extraperitoneal space with an overlap of at least 3–4 cm. The peritoneum is sutured above the prosthesis.

Figure 8.

The obturator orifice (A) is repaired with direct intra-abdominal suture (B). (with permission from Ref. [3]).

5.3 Inguinal approach

The procedure is similar to the Stoppa inguinal hernia repair. Through a median or Pfannenstiel incision, the Retzius’ space is dissected, posterior to the pubic symphysis, the dissection is extended laterally to the antero-superior iliac spine. The peritoneum is detached from the anterior abdominal wall and the epigastric vessels are left attached. Once the sac is reduced in the abdomen, it is possible to place a large prosthesis covering the inguinal, femoral and obturator region attached to the transverse and rectus abdominis muscles medially and on the pubic symphysis inferiorly.

5.4 Femoral approach

A 10-cm vertical incision is made on the medial margin of the femoral triangle medial to the femoral vessels and adductor muscles, passed by blunt dissection between the pectinate and middle adductor muscles. The sac can be resected and the orifice closed with a plug or direct suture. This approach is not the recommended one [3].

Other possible approaches can be performed via combined abdomino-crural, cruro-obturator, inguino-obturator, subcrural intraperitoneal [33, 34, 35]. The obturator dimple can be repaired using a direct suture (Figure 9), with a recurrence rate lower than 3%, or use a resorbable mesh or plug [36, 37]. Patches of peritoneum or omentum may be used in cases of small orifices [38, 39].

Figure 9.

Primary laparoscopic repair by using non-absorbable suture. (with permission from Ref. [4]).

6. Conclusion

Due to its rarity of presentation obturator hernia presents a diagnostic challenge and should be included in the differential diagnosis of intestinal obstruction of unknown origin, especially in emaciated elderly women with chronic disease; a prompt suspect based on aspecific symptoms is crucial for the diagnosis. CT scan has a major sensitivity than other radiological exams. Late diagnosis of obturator hernia can lead to ischemia and bowel necrosis with bowel perforation and then localized or generalized peritonitis as a life-threatening condition. Postoperative complications have been reported in 11.6% of patients as pneumonia, sepsis, wound infection [40, 41] and mesh migration which may be prevented with metal anchors [42, 43]. The resultant morbidity and mortality rates are around 38% and 12–70%, respectively. Surgical management depends on early diagnosis and it is the only possible treatment for this pathology [4].

Acknowledgments

This work has been funded by AUSL Piacenza, Unit of Research and Quality.

Dr. Conti conceived the book chapter; Dr. Conti and Dr. Bonfili wrote the chapter and processed the images. Dr. Baldini and Dr. Conti performed the surgery. Dr. Cattaneo, Dr. Grassi, Dr. Banchini and Dr. Capelli reviewed the literature. All authors reviewed and approved the chapter.

Conflict of interest

The authors declare no conflict of interest.

Notes/thanks/other declarations

We would like to thank the physicians of the Acute Care Surgery team of AUSL Piacenza, Dr. Sonia Agrusti, Dr. Mauro Filosa, Dr. Luigi Percalli, Dr. Gabriele Regina, Dr. Giandomenico Arzu, Dr. Giancarlo Giannone and Dr. Antonio Caizzone for their contributions and expertise in the field of hernia surgery.

We would also like to thank the editor Elsevier-Masson, SAS Paris, for the kind permission to reuse the iconography from the EMC Surgical techniques book.