Introduction

Lumbar hernias are uncommon defects of the posterior abdominal wall caused by the protrusion of extraperitoneal or intraperitoneal contents (1, 2). These hernias constitute only 2% of all abdominal wall hernias (2). They are classified as congenital (20%) and acquired; the latter can be primary (55%) or secondary (25%) (3-5). Posterior abdominal wall hernias are classified as subcostal (L1), flank (L2), iliac (L3), and lumbar (L4) (5). The latter include Grynfeltt hernia (HG), located in the Grynfeltt-Lesshaft triangle, and Petit hernia, located in the Jean-Louis Petit triangle (5-8). Due to their proximity, L4 hernias can affect the L1, L2, and L3 regions if not treated promptly, weakening a larger area of the abdominal wall. 
GH was described by Joseph Grynfeltt in 1866 as a primary hernia that protrudes through the posterior abdominal wall at the level of the superior triangle, causing serious complications (1, 2). Its low incidence and the nonspecificity of its clinical manifestations favor diagnostic errors and hinder both its early diagnosis and the standardization of therapeutic strategies, resulting in a high risk of complications (3). Only about 300 cases of primary lumbar hernias are reported in the literature (1, 3, 5), although this figure needs updating due to the publication of new case reports. Because of its rarity, there is no standardized surgical approach for GH (6). We present a case of GH whose clinical diagnosis was a challenge, highlighting the fundamental role of computed tomography (CT) in establishing the diagnosis and guiding surgical planning.

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Case Presentation

A 60-year-old male patient with a history of hypertension controlled with losartan (50 mg daily) and prior surgical treatment for an inguinal hernia 1 year prior was referred from primary care with an initial ultrasound diagnosis of a lipoma in the right lumbar region.
During the surgical consultation, the patient reported an intentional weight loss of 12 kg over 6 months (decreasing his body mass index from 29.9 to 26 kg/m2), associated with a low-calorie diet as part of antihypertensive treatment initiated 2 years prior. He also noticed a progressively increasing volume in the right lumbar region, which was occasionally accompanied by pain during physical exertion. The patient also reported having little physical activity following the surgery performed for the inguinal hernia.
The physical examination revealed a tender, irreducible mass approximately 4 cm in diameter located at the lower border of the 12th rib in the right lumbar region. Preoperative laboratory tests were within normal limits. A soft tissue ultrasound described a solid, encapsulated, slightly hypoechoic mass in the subcutaneous tissue consistent with a lipoma.
The location of the mass, its irreducibility, and the ultrasound diagnosis of lipoma posed a diagnostic challenge that was clarified by abdominal CT. This study allowed the diagnosis of a GH, revealing a 2-cm hernial ring in the right upper lumbar triangle with a 4-cm diameter hernial sac (Figure 1A and B).

Figure 1.

Abdominal computed tomography scan showing a GH. (A) Axial slice showing the hernia with perirenal fat content, indicated by the yellow arrow. (B) Sagittal slice identifying the GH, indicated by the yellow arrow.

After confirming the patient’s clinical stability and obtaining their informed consent after explaining all the details of the surgery, the surgical intervention was planned. Antibiotic prophylaxis was administered, and under spinal anesthesia, an incision was made parallel to the lower border of the 12th rib at the level of the hernial defect identified by CT scan. During the layered dissection of the hernial sac in the right lumbar region, significant thinning of the posterior abdominal wall was observed. The anatomical distortion secondary to the hernia can hinder its precise identification, which explains why these structures are not always clearly recognizable during surgery. The dissection was performed through the weakest muscle fibers at the level of the hernia (Figure 2A).

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Figure 2.

Surgical site. (A) The hernial sac containing retroperitoneal fat is visible in the center, surrounded by the posterior border of the external oblique muscle (blue arrow), the superior border of the latissimus dorsi muscle (red arrow), and the inferior border (orange arrow). (B) Mesh is placed in the retroperitoneal plane.

The hernia was then fully reduced to the intra-abdominal side, and a 5-cm plane was bluntly dissected around the hernial defect in the retroperitoneum. A lightweight polypropylene mesh, 12 cm in diameter, was placed in the dissected plane and fixed to the muscles with four sutures. Figure 2B shows the mesh in place before layered closure. Given the patient’s satisfactory clinical progress, he was discharged the following day, with no evidence of adverse events or complications. During outpatient follow-up, the patient remains free of recurrence and other complications 2 years after the procedure, with a favorable prognosis.

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Discussion

Grynfeltt hernias have been associated with factors that increase intra-abdominal pressure, such as chronic lung disease, ascites, and pregnancy, as well as with conditions that weaken the abdominal wall, including debilitating chronic diseases, muscle atrophy, weight loss, and aging (1, 3, 4). Anatomically, a Grynfeltt hernia originates in the superior lumbar triangle, bounded by the serratus posterior inferior muscle and the twelfth rib (superior border), the posterior border of the internal oblique abdominal muscle (anterior border), and the anterior border of the erector spinae muscle (posterior border) (3, 4, 8-10). The transversus abdominis aponeurosis forms the floor, and the latissimus dorsi and external oblique muscles form the roof (7, 10). The incidence of this condition is highest between the 50 and 70 years of age (7), while secondary forms are usually related to trauma, abscesses, and surgical incisions (4). In this case, advanced age, weight loss, and muscle atrophy associated with sedentary lifestyle were the main predisposing factors for the development of the hernia.
The diagnosis of a GH requires a high degree of clinical suspicion due to its rarity and nonspecific presentation, as it can be confused with other conditions (2, 7). In the case presented here, the primary care physician initially interpreted the lesion as a lipoma based on its subcutaneous location, the absence of protrusion during the Valsalva maneuver, and the ultrasound findings. However, at the hospital level, a lumbar hernia was suspected based on the clinical history obtained during the patient interview, its location within the superior lumbar triangle, and the professionals’ prior experience. The presence of a small hernia defect associated with adhesions was considered, which would explain the irreducibility of the lesion. Establishing a differential diagnosis for masses of the posterior abdominal wall is paramount; it includes among others lipomas, hematomas, abscesses, renal masses, and soft tissue tumors (1). Failure to consider this entity can lead to diagnostic errors and inappropriate therapeutic decisions (3, 5).
Abdominal ultrasound is sometimes inconclusive for the diagnosis of GH, especially when the hernial defect is small and there is no obvious protrusion, which could lead to confusion with subcutaneous tissue lesions such as lipomas (1-3). In contrast, CT is the imaging study of choice due to its 98% sensitivity, which allows for the detection of musculoaponeurotic defects and other hernial details (1, 2, 4). The findings are often diverse, including retroperitoneal fat, omentum, kidney, spleen, appendix, small or large intestine, among other structures (3, 7). In the presented clinical case, CT accurately revealed the hernial defect with a hernial sac containing retroperitoneal fat (Figure 1A and B), which contributed to surgical planning. These background studies highlight the key role of CT in the identification of posterior abdominal wall hernias, consolidating itself as the reference imaging modality for the diagnosis and surgical planning of HG (4).
Surgical intervention is the treatment of choice for gestational hernias (GHs) due to the risk of complications, including incarceration (25%) and strangulation (8-10%) (2-4). The surgical approach should be individualized based on the characteristics of the hernia, the experience of the surgical team, and available resources (4, 6). Repair can be performed using open or minimally invasive techniques, although there is no standardized procedure due to the low incidence of this condition (1, 5, 9). In cases of vascular compromise or complex hernias, the open approach is usually the preferred option; while small primary hernias are candidates for the minimally invasive extraperitoneal approach (1, 5, 6). Furthermore, the closure of the defect can be technically complex due to the proximity of bone structures (10). Minimally invasive techniques offer advantages such as less tissue dissection, better visualization of nerve structures, less postoperative pain, and a shorter hospital stay (1, 6, 9). The retroperitoneal endoscopic approach avoids the mobilization of intraperitoneal viscera, although it presents a limited surgical field and certain difficulties for the use of instruments; whereas the transabdominal approach requires mobilization of the colon. (6, 9).                      
Regardless of the approach used, the use of prosthetic mesh significantly reduces recurrence rates (9). The choice of mesh type depends on the surgical approach: extraperitoneal repairs are usually performed with lightweight, uncoated meshes, while intraperitoneal approaches require coated meshes to minimize the formation of visceral adhesions (1, 4). In this case, an open repair with polypropylene mesh was chosen, considering the availability of resources. This approach continues to be widely used, especially in settings with limited access to minimally invasive techniques. According to the literature, it has recurrence and complication rates comparable to those of minimally invasive approaches; its main disadvantage is the aesthetic impact (7, 9).
This study has the inherent limitations of its descriptive design, as it involves only one case, preventing comparison of results between different surgical techniques. The 2-year postoperative follow-up is adequate but insufficient for the assessment of late complications.

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Conclusion

A Grynfeltt hernia is an uncommon entity that poses a diagnostic challenge due to its nonspecific clinical presentation and should be suspected in the presence of a mass in the superior lumbar triangle. CT proved to be an effective imaging modality for demonstrating the GH and its boundaries, as well as for surgical planning.

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Author contributions
Both authors equally contributed to conceptualization, data curation, formal analysis, investigation, methodology, supervision, validation, visualization and in writing, reviewing & editing of the original draft.

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References​​

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