Germán Castrillón

Multidetector Computed Tomography of Penetrating Abdominal Trauma

Although there is no debate that patients with peritonitis or hemodynamic instability should undergo urgent laparotomy after penetrating injury to the abdomen, it is also clear that certain stable patients without peritonitis may be managed without the need for an operation. The practice of deciding which patients may not need surgery after penetrating abdominal wounds has been termed “non-operative management.” This practice has been readily accepted during the past few decades with regard to abdominal stab wounds; however, controversy persists regarding when a conservative management approach is appropriate for penetrating gunshot wounds. Abdominal gunshot injuries are still commonly treated with mandatory exploration because of the multiple reports emphasizing a high incidence of significant injuries and the complications that result from a missed injury or a delayed diagnosis. The enthusiasm for nonoperative management in patients with penetrating abdominal trauma is based on a relatively high incidence of nontherapeutic or negative laparotomy from civilian low-velocity injuries. Reports on the incidence of unnecessary laparotomies range from 23% to 53% for patients with stab wounds and 5.3%-27% for patients with gunshot wounds.1 Complications develop in 2.5%-41% of all trauma patients undergoing unnecessary laparotomy, and small bowel obstruction, pneumothorax, ileus, wound infection, myocardial infarction, visceral injury, and even death have been reported secondary to unnecessary laparotomy. 2,3 The process of selecting patients for nonoperative management requires considering several factors: the specific mechanism (stab vs gunshot), the velocity of the inflicting agent (low vs high), and the different areas of the torso that may be affected (intraperitoneal, retroperitoneal, and thoracoabdominal). In developing management strategies for penetrating abdominal trauma, it is helpful to divide the abdomen into regions: the anterior abdomen (from xiphoid to pubis, between the anterior axillary lines); the flank and back (posterior to the anterior axillary lines); and the thoracoabdomen (from the nipple line to the costal margin). The approach for each of these regions varies. If the patient is selected for initial nonoperative management, additional diagnostic methods often become necessary. An abdominopelvic multidetector computed tomography is now strongly regarded as the main diagnostic tool to facilitate initial management decisions. However, other methods that can be considered include diagnostic peritoneal lavage, ultrasonography (US), and laparoscopy.

Use of DWI in Female Pelvis

Multiple applications of DWI in the female pelvis have been described, and some have demonstrated to be of considerable practical utility. Studies have found that the mean ADC values can be used to differentiate between normal and cancerous tissue in the uterine cervix, with little overlap. Squamous cell carcinoma tends to have lower ADC values than adenocarcinoma and normal tissue has higher ADC values than both primary malignancies. Cervical tumors with higher cellular density and higher histologic grade show a tendency towards lower ADC values compared with those of tumors with lower histologic grade and lower cellular density, which have higher ADC values. The ADC values in uterine cervical cancer increases after chemotherapy and/or radiation therapy and, therefore, following the ADC values through the course of treatment may add to the value of MRI for monitoring response to therapy. Besides, DWI has recently demonstrated its capacity to distinguish between metastatic and hyperplastic lymph nodes using ADC quantifications, with significant lower ADC values for metastatic lymph nodes. Data are accumulating to support the use of DWI as a tool to detect endometrial carcinoma and to differentiate benign from malignant lesions. For example, ADC values of endometrial carcinoma are lower than the ADC values of endometrial polyps, submucosal leiomyomas, and normal endometrial tissue. Hyperintensity of endometrial tumors on DWI improves the visualization of depth of tumor invasion. Besides, ADC values are useful for differentiation of degenerated leiomyomas and normal myometrium from the rare malignant uterine sarcomas. DWI has also showed its potential as an adjunt for assessing treatment of uterine fibroids. The ADC values of malignant ovarian tumors vary widely, a phenomenon that is attributable to their heterogeneous histology and morphology, limiting its utilization in the characterization of ovarian masses. DWI has demonstrated high sensitivity in the detection of small metastatic peritoneal deposits of ovarian cancer due to high CNR, even in challenging anatomical areas.

Diffusion-Weighted Imaging of the Gastrointestinal Tract and Peritoneum

The use of DWI to evaluate the gastrointestinal tract has been studied less extensively than in solid abdominal organs and, consequently, there is less evidence to support the use of DWI in such cases. Because primary and recurrent malignancies and inflammatory diseases of the bowel wall both increase the wall thickness, DWI is a useful tool to differentiate between the two entities, with distinct advantages over conventional MR images. Furthermore, colon carcinomas show lower ADC values than active or fibrotic inflammatory bowel disease. Several studies have also reported that DWI is a successful method to predict response to and evaluate the efficacy of treatment of colorectal carcinoma. As it may be expected, gastric and intestinal adenocarcinoma and lymphoma show restriction of the free water diffusion. Besides, with the available preliminary data, DWI performs equivalently to CT in detection and staging of patients with gastric cancer. Common everyday uses of MR in gastrointestinal diseases include pregnant patients with acute abdominal pain and suspected acute appendicitis and patients with Crohn disease in remission who require periodic surveillance with imaging or who present with acute flares and possible complications. In these patients, DWI is a useful tool as acute appendicitis and areas with active inflammatory disease will show restricted diffusion. In a similar fashion, acute diverticulitis will show high signal intensity with high b values and low ADC values. Furthermore, DWI has been also used to evaluate peritoneal metastasis due to its higher sensitivity to detect small deposits against a suppressed background. Recent data has shown higher sensitivity, specificity, and accuracy for the detection of peritoneal metastasis with the addition of DWI with high b value to standard MRI protocols.

Diffusion-Weighted MR Imaging of the Pancreas

Publications exploring the use of DWI for evaluation of pancreatic disease are limited in number and scope. However, the value of DWI in various pancreatic conditions continues to be explored and available results suggest that there will likely be a niche for this technique in the clinic. Available studies have shown that the measured ADC values of the normal pancreatic glandular parenchyma on DWI vary considerably and are determined by factors such as age, the anatomic portion of the gland, and magnet field strength. Normal pancreas has significantly higher mean ADC than pancreatic cancer or mass-forming pancreatitis. Furthermore, proper use of DWI may aid in the differentiation of focal pancreatitis from ductal adenocarcinoma. Besides, in patients with known pancreatic cancer, the benefits of DWI include improved characterization of enlarged lymph nodes, detection of peritoneal carcinomatosis, and detection of distant (such as hepatic) metastases. It is also possible that ADC measurements can be used as a quantitative tool for predicting and monitoring tumor response. There is some data that supports the use of DWI for characterizing and determining the significance of pancreatic cystic lesions. There is still very little published scientific data to support the use of DWI in the gallbladder and biliary tract, although cholangiocarcinoma exhibits diffusion restriction, which is helpful for separating the lesion from the surrounding hepatic parenchyma, and neoplastic and inflammatory diseases of the gallbladder can also be evaluated with MR.

Hepatic transplantation in a child with giant multicystic tumor: Pathological and imaging findings

Castrillon GA, Sepúlveda E, Yepez NL, Hoyos S, Osorio G. Hepatic transplantation in a child with giant multicystic tumor: Pathological and imaging findings. Pediatr Transplantation 2010: 14:e58–e61.