XMU-MP-1 The mechanisms of abdominal blunt
The mechanisms of abdominal blunt trauma, that cause intestinal perforation in the hernia sac, have received various explanations. Reynolds asserted that direct trauma to an inguinal hernia can produce enough pressure to cause perforation of the intestinal walls. A study by O’Leary and MacGregor showed rapid elevation of intra-abdominal pressure as high as 300mmHg, exceeding the 150mmHg to 260mmHg needed to perforate an intestinal loop in experimental models; this could be the cause in our patient. Another XMU-MP-1 is that sheering forces occur between the bowel in the hernia and its fixation point on the mesentery, causing the bowel wall to stretch and tear. We believe that the underlying mechanism in this case was the elevation of intra-abdominal pressure, which probably led to increased intraluminal pressure in the segment of the intestine adjacent to the hernia, the increased pressure gradient causing the intestinal loop to blow out over the aperture.
The diagnosis of small bowel perforation can be very challenging. It is based on the history, mechanism of injury, and serial physical examination. A CT scan and ultrasound can be performed, but the predictive ultrasound is of positive value in the diagnosis of blunt small bowel injury (SBI) in only 38% of cases and the false-negative rate for the CT scan in diagnosing perforated SBI is about 13%. Thus, a CT scan and ultrasound cannot be relied upon to rule out perforated SBI. In our case, the initial CT scan did not show any obvious finding, and therefore a delayed or missed diagnosis would have been made if it had been taken as definitive.
Case report Due to the relatively long duration of the abdominal pain, an abdominal ultrasound was conducted which showed a hypoechoic tumor in the left kidney. A computed tomography (CT) scan revealed a large heterogeneous tumor (8.3 × 5.9 cm) at the lower pole of the left kidney that was invading into the perirenal fat but not extending beyond Gerota\'s fascia (Fig. 1). Lymphadenopathy and venous thrombosis were absent. A bone scan revealed the absence of bone metastasis. Based on the tentative diagnosis of renal cell carcinoma (cT2N0M0), a retroperitoneal laparoscopic radical nephrectomy was performed. On hemisection of the kidney, a firm tumor measuring 8 × 6 cm with a whitish gray whorled appearance was found in the lower pole of the left kidney (Fig. 2). The major renal vessels, lymph nodes, and ureter were grossly disease-free. Upon microscopic examination, the tumor was found to have spindle cells with a degree of high cellularity and an interlacing fascicular pattern. Most tumor cells generally had blunt-ended nuclei and eosinophilic cytoplasm (Fig. 3). Nuclear atypia and even bizarre giant tumor cells were occasionally seen as well. Immunohistochemical analysis showed that the tumor cells were diffusely positive for smooth muscle actin (Fig. 4), focally positive for desmin (Fig. 5), and negative for cytokeratin, c-kit, and HMB45. According to the scoring system of the French Federation of Cancer Centers, scores of 1 were assigned for tumor differentiation, necrosis, and mitosis. A total score of 3 was therefore recorded, defining this as a grade I tumor.
Discussion Leiomyosarcoma is a malignant tumor that arises from the smooth muscle components of the soft tissue and commonly occurs in the retroperitoneum. However, primary renal leiomyosarcoma is rare in the kidney. It can occur in the renal capsule, pelvis, parenchyma, and renal vessels. There is predominance in female, with most cases diagnosed in the fourth to sixth decades of life. The mean tumor size at the time of diagnosis is 13.4 cm, and about 60% of tumors are located on the right kidney. The most common clinical presentations are an abdominal mass (with or without tenderness) that is accompanied by hematuria and, less frequently, weight loss and gastrointestinal symptoms. Its usual appearance on CT is fibrous tissue with a predominance of spindle cells. The fibrous tissue exhibits low attenuation on early postcontrast CT and high attenuation on delayed postcontrast CT. Conversely, the spindle cell components of leiomyosarcoma exhibit high attenuation on early postcontrast CT and low attenuation on delayed postcontrast CT. Because of its nonspecific symptoms and the potential confusion that can result from imaging techniques, preoperative diagnosis is difficult. Fine needle aspiration has been used in some cases.