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This article reviews the computed tomography (CT) findings of miscellaneous regional and diffuse small bowel disorders. CT technique and potential pitfalls are discussed. Several categories of regional and diffuse small bowel conditions are reviewed, with representative CT images. These disorders often have relatively nonspecific CT appearances, and correlation with the history, clinical, and laboratory findings in each specific case is critical. In selected conditions, the CT findings are highly specific. The imaging literature of some of the common as well as some of the less common entities is reviewed, and clues to narrowing the differential diagnosis are provided.

A broad spectrum of skin and subcutaneous (SQ) findings may be discovered in the emergency setting on CT examinations. There are some findings that are directly relevant to the reason or reasons why the patient has undergone the CT examination. However, other findings may be incidental. The skin and SQ tissues are by definition on the periphery of CT images and may be overlooked by the radiologist, although findings related to them can be of clinical importance. The purpose of this pictorial essay is to present a broad spectrum of skin and subcutaneous findings which may be identified on CT examinations in the emergency setting (and in some cases nonemergently), and to briefly review the relevant imaging literature, which surprisingly is relatively limited on this topic. Categories of cutaneous and subcutaneous abnormalities that will be covered include trauma and hemorrhage, iatrogenic findings, infection, neoplasms, calcification, and other miscellaneous entities, all of which may initially present on emergency CT examinations of the body.

Cesarean scar pregnancies (CSPs) are a relatively rare form of ectopic pregnancy in which the embryo is implanted within the fibrous scar of a previous cesarean section. A greater number of cases of CSPs are currently being reported as the rates of cesarean section are increasing globally and as detection of scar pregnancy has improved with use of transvaginal ultrasound (TVUS) with color Doppler imaging. Delayed diagnosis and management of this potentially life-threatening condition may result in complications, predominantly uterine rupture and hemorrhage with significant potential maternal morbidity. Diagnosis of a cesarean scar pregnancy (CSP) requires a high index of clinical suspicion, as up to 40% of patients may be asymptomatic. TVUS has a reported sensitivity of 84.6% and has become the imaging examination of choice for diagnosis of a CSP. Magnetic resonance imaging (MRI) has been used in a small number of patients as an adjunct to TVUS. In the present report, MRI is highlighted as a problem-solving tool capable of more precisely identifying the relationship of a CSP to adjacent structures, thereby providing additional information critical to directing appropriate patient management and therapy.

Because virtually all patients with colonic cancer will undergo some form of surgical therapy, the role of preoperative imaging is directed at determining the presence or absence of synchronous carcinomas or adenomas and local or distant metastases. In contrast, preoperative staging for rectal carcinoma has significant therapeutic implications and will direct the use of radiation therapy, surgical excision, or chemotherapy. CT of the chest, abdomen, and pelvis is recommended for the initial evaluation for the preoperative assessment of patients with colorectal carcinoma. Although the overall accuracy of CT varies directly with the stage of colorectal carcinoma, CT can accurately assess the presence of metastatic disease. MRI using endorectal coils can accurately assess the depth of bowel wall penetration of rectal carcinomas. Phased-array coils provide additional information about lymph node involvement. Adding diffusion-weighted imaging to conventional MRI yields better diagnostic accuracy than conventional MRI alone. Transrectal ultrasound can distinguish layers within the rectal wall and provides accurate assessment of the depth of tumor penetration and perirectal spread, and PET and PET/CT have been shown to alter therapy in almost one-third of patients with advanced primary rectal cancer. The ACR Appropriateness Criteria((R)) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Implantation of an endometriotic lesion within a pelvic or abdominal wall scar is an uncommon but well-described condition that may be the underlying cause of acute or chronic recurrent abdominal or pelvic pain, especially after cesarean section. Radiologists may not consider scar endometriosis when it is encountered at cross-sectional imaging. Cesarean section scars are the most common site of extraovarian or extrauterine endometriosis. The condition also has been identified in other uterine surgery-related scars and in the skin, subcutaneous tissues, and abdominal and pelvic wall musculature adjacent to these scars. The most plausible cause of scar endometriosis is implantation of endometrial stem cells at the surgical site at the time of uterine surgery. Patients with scar endometriosis may be asymptomatic or present with cyclical pain corresponding to the menstrual cycle. Cross-sectional imaging findings vary from the nonspecific to those suggestive of the diagnosis when combined with clinical history. In particular, the presence of blood products in an anterior abdominal wall mass at magnetic resonance (MR) imaging with no other explanation is strongly suggestive of scar endometriosis. Ultrasonography, computed tomography, and MR imaging may be used to depict an endometriotic lesion, exclude endometriosis, or provide evidence for an alternative diagnosis.

Often patients with fevers of unknown origin (FUOs) present with loss of appetite, weight loss, and night sweats, without localizing signs. Some are found to have a renal mass during diagnostic evaluation. In patients with FUOs and a renal mass, the differential diagnosis includes renal tuberculosis, renal cell carcinoma (hypernephroma), renal malakoplakia, and xanthogranulomatous pyelonephritis. A 68-year-old woman presented with an FUO during her diagnostic workup. She manifested an irregularly enlarged kidney on abdominal computed tomography (CT) scan, as well as a highly elevated erythrocyte sedimentation rate of more than 100 mm/hour, an elevated serum ferritin level, and chronic thrombocytosis, which favored a diagnosis of renal cell carcinoma. Renal malakoplakia and renal tuberculosis comprised further differential diagnostic considerations. Microscopic hematuria may be present with any of the disorders in the differential diagnosis, but was absent in this case. An abdominal CT scan was suggestive of xanthogranulomatous pyelonephritis. Because of concerns regarding renal cell carcinoma, the patient received a nephrectomy. The pathologic diagnosis was of xanthogranulomatous pyelonephritis, without renal cell carcinoma.

Computed tomographic colonography (CTC) is a relatively new imaging modality for the examination of patients for colorectal polyps and cancer. It has been validated in its accuracy for the detection of colon cancer and larger polyps (more than likely premalignant). CTC, however, is not widely accepted as a primary screening modality in the United States at present by many third-party payers, including Medicare, and its exact role in screening is evolving. Moreover, there has been opposition to incorporating CTC as an accepted screening instrument, especially by gastroenterologists. Heretofore, optical colonoscopy has been the mainstay in this screening. We discuss these issues and the continuing controversies concerning CTC.

Various disorders of sex development (DSD) result in abnormal development of genitalia, which may be recognized at prenatal ultrasonography, immediately after birth, or later in life. Current methods for diagnosing DSD include a thorough physical examination, laboratory tests to determine hormone levels and identify chromosomal abnormalities, and radiologic imaging of the genitourinary tract and adjacent organs. Because of the complex nature of DSD, the participation of a multidisciplinary team is required to address the patient's medical needs as well as any psychosocial issues that the patient or the family may encounter after the diagnosis. The first step in the management of DSD is sex assignment, which is based on factors such as the genotype; the presence, location, and appearance of reproductive organs; the potential for fertility; and the cultural background and beliefs of the patient's family. The primary goal of sex assignment is to achieve the greatest possible consistency between the patient's assigned sex and his or her gender identity. Once the sex is assigned, the next step in management might be surgery, hormone therapy, or no intervention at all. Patients with ovotesticular DSD and gonadal dysgenesis may require a gonadectomy, followed by reconstructive surgery. Some patients may need hormone replacement therapy during puberty. An understanding of the immediacy of families' need for sex assignment and clinicians' need for reliable diagnostic imaging results will help radiologists participate effectively in the prenatal and postnatal assessment of patients with DSD.

Cutaneous presentations of bronchogenic cysts are rare in all age groups. Previous reports of cutaneous manifestations of bronchogenic cysts have been described as nodular, adherent masses, most frequently with a suprasternal location. We report a unique presentation of an infant with a pedunculated, anterior chest wall mass, which was identified as a bronchogenic cyst.

Segmental testicular infarction is a relatively rare acute or subacute condition which is infrequently thought of in the differential diagnosis for testicular pain. However, missing or misdiagnosing this entity on clinical evaluation and/or imaging has significant implications for patients as they may undergo unnecessary surgery for suspected testicular torsion or tumor. Knowledge and recognition of the features of segmental testicular infarction on ultrasound and MRI will aid in the diagnosis of this disease early in the patient's course. The common imaging features of segmental testicular infarction and the clinical literature are reviewed, with an emphasis on ultrasound, utilizing seven recent cases from three institutions.