Bowel Diseases
Synonyms/Description
Pelvic masses related to bowel such as appendicitis, endometriosis, colon cancer, Crohn’s disease, ulcerative colitis, diverticulitis, lymphoma, sarcoma, or other bowel-specific diseases identified on a pelvic ultrasound
Etiology
There are multiple etiologies in this grouping of bowel diseases. The etiologies range from inflammatory/infectious such as appendicitis, inflammatory bowel diseases, and diverticulitis to neoplasms such as lymphomas, carcinomas, and sarcomas.
In the small bowel, neuroendocrine tumors, adenocarcinomas, sarcomas, lymphomas, and miscellaneous tumors comprise 36.5%, 30.9%, 10.0%, 18.7%, and 3.9% of malignancies, respectively. In the appendix, neuroendocrine tumors, adenocarcinomas, sarcomas, lymphomas, and miscellaneous tumors comprise 31.7%, 65.4%, greater than 1%, 1.7%, and 1.1% of malignancies, respectively. Colon tumors include mostly adenocarcinomas (93.0%), whereas sarcomas and lymphomas are relatively rare.
These entities are briefly discussed in terms of ultrasound findings because they may be encountered during a sonographic gynecologic exam. For more detailed information about any of these lesions, please refer to the suggested reading.
Ultrasound Findings
Diseases of the bowel are detectable and can be accurately diagnosed using ultrasound. Typically the sonographic evaluation of bowel abnormalities includes the appearance of the bowel wall, amount and quality of peristalsis, reaction to manual compression using the transducer, and relative “stiffness” of the bowel loop. Also there may be a nonspecific mass, which is difficult to distinguish from adnexal or uterine masses. It is crucial to identify the uterus and ovaries separate from the mass to correctly diagnose it as a bowel problem.
Endometriosis
Endometriosis of the rectosigmoid colon is covered in the section on endometriosis.
Appendicitis
The typical ultrasound findings include a distended, noncompressible tubular mass, greater than 7 mm in diameter and with relatively cystic center suggesting bowel. In the transverse view, the abnormal appendix often appears as a double ring indicating the swollen wall. Gentle compression will displace normal loops of bowel to better demonstrate the inflamed appendix, although the compression is usually uncomfortable for the patient. There can also be inflammation of the adjacent omental fat with a very echogenic characteristic appearance, sometimes with shadowing from an appendicolith. The sensitivity for ultrasound compared with computed tomography to diagnose appendicitis is 75% versus 90%, and the specificity is 86% versus 100%. Ultrasound is often the only imaging needed to make the diagnosis.
Inflammatory Bowel Diseases
These include Crohn’s disease and ulcerative colitis, which typically produce a diffuse thickening of a segment of bowel wall, with reduced peristalsis and a “stiff-looking,” relatively straight segment of bowel. There is usually a loss of the normal striated gut appearance because of the disease involving multiple layers of the bowel wall. Ulcerative colitis is found mostly in the rectum and rectosigmoid, whereas Crohn’s is typically seen in the distal ileum.
Diverticulitis
When a diverticulum becomes inflamed, it appears sonographically as a segmental area of thickened bowel wall with an inflamed outpouching (diverticulum) and inflamed surrounding pericolic fat. Diverticulitis can also result in an abscess that can be seen sonographically. The bowel wall thickening is usually asymmetric but retains its normal three layers, thus differentiating it from the appearance of inflammatory bowel disease.
Duplication Cyst
Bowel duplication cysts are rare congenital anomalies that may be asymptomatic for much of a person’s life. However, when these undergo hemorrhage, infection, or torsion, the symptoms are similar to appendicitis or ovarian torsion. Sonographically, when these cysts are symptomatic, they will show internal hemorrhage and appear similar to an endometrioma.
Lymphoma
Lymphomas of the bowel wall are typically B-cell tumors and usually involve the small intestine in the region of the distal ileum. The ultrasound appearance is that of a bulky circumferential irregular wall thickening with occasional dilation of the bowel and lymph node enlargement.
Colon Cancer
Adenocarcinoma is the most common malignant tumor of the colon. The ultrasound appearance is that of a hypoechoic mass with many tiny echogenic septations, some areas of calcification, and a bubbly or airy texture. In many cases, the original loop of colon affected is difficult to see sonographically and often the mass is not initially attributed to the bowel.
Gastrointestinal Stromal Tumor
These are a group of mesenchymal sarcomas that arise typically from the muscularis mucosa of the bowel wall and are therefore submucosal. Gastrointestinal stromal tumors (GISTs) are homogeneous soft-tissue solid masses that may be small or grow into a large necrotic, heterogeneous mass. They are usually malignant tumors that can metastasize to the liver.
Differential Diagnosis
The main differential diagnosis for a tender mass in the right lower quadrant includes appendicitis as well as many gynecologic etiologies such as hydrosalpinx, hemorrhagic cyst, or degenerating fibroid. It is important to view the mass transabdominally as well as transvaginally to get a better sense of its location. As previously discussed, identifying the uterus and ovaries separately from the mass is essential to making the correct diagnosis.
A thickened loop of bowel suggests a more diffuse diagnosis such as lymphoma or chronic inflammatory disease. A focal area of bowel wall nodularity or thickening may indicate an endometriotic implant or diverticulitis. (A careful history may help differentiate these diagnoses.) A solitary mass separate from the uterus or ovaries may represent a bowel tumor such as a leiomyoma, sarcoma, or adenocarcinoma. A cyst separate from the ovary or tube may represent a bowel duplication cyst, although these can be confused with endometriomas.
Clinical Aspects and Recommendations
Ultrasound should be the first test done in patients suspected of having appendicitis and is often sufficient to make an accurate diagnosis. In many cases of bowel malignancy or chronic inflammatory disease, other imaging modalities and procedures are necessary to arrive at the correct diagnosis, and the treatment and prognosis depend on the final diagnosis. However, ultrasound may be the entry point at which patients with various bowel problems enter the medical care system, and it is important to keep these diagnoses in mind when performing pelvic ultrasound.
Figures
Videos
Video 1 on bowel-related masses is available online.
Suggested Reading
Ackerman S.J., Irshad A., Anis M. Ultrasound for pelvic pain. II: Nongynecologic causes. Obstet Gynecol Clin North Am.. 2011;38:69–83.
Gustafsson B.I., Siddique L., Chan A., Dong M., Drozdov I., Kidd M., Modlin I.M. Uncommon cancers of the small intestine, appendix and colon: an analysis of SEER 1973-2004, and current diagnosis and therapy. Int J Oncol.. 2008;33:1121–1131.
Hughes J.A., Cook J.V., Said A., Chong S.K., Towu E., Reidy J. Gastrointestinal stromal tumour of the duodenum in a 7-year-old boy. Pediatr Radiol. 2004;34:1024–1027.
Lee N.K., Kim S., Kim G.H., Jeon T.Y., Kim D.H., Jang H.J., Park D.Y. Hypervascular subepithelial gastrointestinal masses: CT-pathologic correlation. RadioGraphics. 2010;30:1915–1934.
Linam L.E., Munden M. Sonography as the first line of evaluation in children with suspected acute appendicitis. J Ultrasound Med. 2012;31:1153–1157.
Maturen K.E., Wasnik A.P., Kamaya A., Dillman J.R., Kaza R.K., Pandya A., Maheshwary R.K. Ultrasound imaging of bowel pathology: technique and keys to diagnosis in the acute abdomen. AJR. 2011;197:1067–1075.
O’Malley M.E., Wilson S.R. Ultrasound of gastrointestinal tract abnormalities with CT correlation. RadioGraphics. 2003;23:59–72.
