Colon


COLON



What is the best next step in the management of this patient?


a. Complete blood count (CBC)


b. Stool occult blood


c. Iron studies


d. Basic metabolic profile


e. Colonoscopy


f. All of the above


Answer f. All of the above


This patient is presenting with signs and symptoms of anemia, and given his age and risk factors most likely has colon adenocarcinoma. The first step is to establish the patient’s cause of fatigue by checking his CBC, iron studies, and kidney function. This should be combined with a stool occult blood test and eventually a colonoscopy if possible. If the patient had presented with melena, an upper endoscopy would have been considered, but given the change in bowel habits and stool caliber, it is likely a left-sided malignancy.






Hematochezia is more often caused by rectosigmoid than right-sided colon cancer.






Given the patient’s family history, when would have been the appropriate screening interval for this patient?


a. Age 40 years and every 5 years thereafter


b. Age 40 years and every 10 years thereafter


c. Age 45 years and every 5 years thereafter


d. Age 45 years and every 10 years thereafter


e. Age 50 years


Answer a. Age 40 years and every 5 years thereafter


The screening interval is normally age 50 years and every 10 years thereafter, if normal, for all patients without a family history. However, in patients who have a first-degree relative with colon cancer, the screening should begin 10 years before the age of the relative or age 40 years, whichever comes first, and should be repeated every 5 years.







Gene changes in colon cancer


• General colon cancer: K-ras mutations


• Familial adenomatous polyposis: APC gene


• Hereditary nonpolyposis colon cancer syndrome or Lynch syndrome: MSH2, MLH1, and PMS2 genes











Colorectal cancer screening with colonoscopy has the highest sensitivity and specificity and reduces mortality rates the most.


Strep bovis endocarditis = Colon cancer = Do colonoscopy as the next step


Orders:


Complete blood count (CBC)


Stool occult blood


Iron studies


Basic metabolic profile (BMP)


Colonoscopy


Gastrointestinal consult


Result: Laboratory study results reveal a hemoglobin of 7.6 g/dL, with low serum iron, ferritin, and a high total iron-binding capacity (TIBC). The stool occult blood test result was positive. The BMP was within normal limits. Colonoscopy revealed a large ulcerated mass in the left lower quadrant (Figure 9-1).






images


Figure 9-1. Colon cancer. (Reproduced, with permission, Greenberger NJ, Blumberg RS, Burakoff R, eds. Current Diagnosis & Treatment: Gastroenterology, Hepatology, & Endoscopy. 2nd ed. New York: McGraw-Hill; 2012.)






In iron deficiency anemia, iron studies will reveal low serum iron, low serum ferritin, and TIBC.











CCS TIP: Computed tomographic colonography (CTC, formerly “virtual colonoscopy”) is always the wrong answer on USMLE Step 3 or CCS.






What is the best next step in the management of this patient?


a. Computed tomography (CT) scan of the chest, abdomen, and pelvis


b. Surgical resection


c. Chemotherapy with a 5-fluorouracil (F-FU)–based regiment


d. All of the above


Answer a. Computed tomography (CT) scan of the chest, abdomen, and pelvis


Before the establishment of a treatment regimen, staging of the colorectal cancer is needed because the stage changes the management plan. Surgical resection combined with chemotherapy is considered to be a part of treatment after a patient has the staging established.






5-FU is a thymidylate synthase inhibitor that in turn causes synthesis of the pyrimidine thymidine to be blocked.










What is the most likely diagnosis?


a. Gastroenteritis


b. Ulcerative colitis


c. Toxic megacolon


d. Ischemic colitis


e. Diverticulitis


Answer c. Toxic megacolon


Patients presenting with severe abdominal distension, dehydration, pain, and fever with diarrhea are likely to have toxic megacolon. There are numerous causes, but this patient’s is Clostridium difficile infection caused by recent antibiotic exposure. Gastroenteritis does present with nausea, vomiting, and diarrhea but is not associated with severe distension and pain. Ulcerative colitis does not present this acutely and would have bloody diarrhea. Ischemic colitis and diverticulitis do not affect a patient this young and would not have a history of antibiotic exposure.






C. difficile is the leading cause of hospital-acquired diarrhea.











In patients with HIV infection or AIDS, cytomegalovirus colitis is the leading cause of toxic megacolon.










The BI/NAP1 strain of C. difficile is the most strongly associated with toxic megacolon.











Saccharomyces boulardii as a probiotic in the treatment of C. difficile is contraindicated in patients taking immunosuppressive medication, who have had recent surgical intervention, or who have had recent prolonged hospitalization.






What is the best next step in the management of this patient?


a. Abdominal radiography


b. C. difficile toxin assay


c. Intravenous (IV) normal saline


d. Complete blood count (CBC)


e. Basic metabolic profile (BMP)


f. All of the above


Answer f. All of the above


In a patient presenting with signs and symptoms of toxic megacolon, the initial management consists of obtaining an abdominal radiography, CBC, C. difficile toxin assay, and resuscitation of the patient with normal saline. A BMP is needed to ensure the patient does not have life-threatening electrolyte imbalances such as hypokalemia and to measure renal function. An abdominal radiography is the best initial test and is used to measure the dilation of the transverse colon, which is most commonly dilated. Dilation of 6 cm or more of is diagnostic of toxic megacolon.







Orders:


Abdominal radiography


C. difficile toxin assay


IV normal saline


CBC


BMP


The CBC reveals a white blood cell (WBC) count of 21,500 cells/mm3, a blood urea nitrogen/creatinine ratio of 36/1.9, and a positive C. difficile toxin assay. Abdominal radiography demonstrates severe large bowel dilation with the transverse bowel measuring 6 cm (Figure 9-2).






images


Figure 9-2. Toxic megacolon with perforation. Supine radiograph demonstrates marked mucosal nodularity and thickening of the transverse colon. (Reproduced, with permission, from Bongard FS, et al. Current Diagnosis & Treatment: Critical Care. 3rd ed. New York: McGraw-Hill; 2008.)


What is the most appropriate therapy for this patient?


a. Surgical consult


b. IV vancomycin


c. Oral vancomycin


d. Oral metronidazole


e. Rectal steroid suppository


f. Oral vancomycin and oral metronidazole


Answer f. Oral vancomycin and oral metronidazole


In patients with toxic megacolon caused by severe C. difficile colitis, the first step is to stop the offending antibiotic, then treat with vancomycin and metronidazole orally. Surgical consult is reserved for patients after 48 to 72 hours of observation under antibiotic therapy. IV vancomycin is always the incorrect answer in the treatment of C. difficile because it does not cross into the bowel from intravascular circulation. Surgery in the form of colectomy is for patients who do not improve within 48 to 72 hours or in those who show evidence of localized perforation.


Dec 22, 2016 | Posted by in GYNECOLOGY | Comments Off on Colon
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