Differential Diagnosis
The patient presents with left-sided abdominal pain, thrombocytosis (elevated platelet count), iron deficiency anemia, and specific findings on CT scan including wall thickening in the proximal ascending colon, prostate enlargement, a possible splenic infarction, and secondary infection. Here's a categorized differential diagnosis:
Single Most Likely Diagnosis
- Colorectal Cancer: The combination of iron deficiency anemia, thrombocytosis, and wall thickening in the proximal ascending colon on CT scan strongly suggests a malignancy, with colorectal cancer being a leading consideration. The anemia could be due to chronic blood loss from the tumor, and thrombocytosis can occur as a paraneoplastic syndrome.
Other Likely Diagnoses
- Diverticulitis: Although the wall thickening is in the ascending colon, which is less common for diverticulitis, the presence of abdominal pain and possible infection (suggested by the splenic findings) could still point towards an inflammatory process like diverticulitis, especially if the patient has a history of diverticulosis.
- Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis could explain the colon wall thickening and abdominal pain. However, IBD typically presents with diarrhea, weight loss, and other systemic symptoms, which are not mentioned here.
- Prostate Cancer: The marked enlargement of the prostate with hypertrophy extending into the urinary bladder base could indicate prostate cancer, especially in the context of the patient's age and gender. Prostate cancer can metastasize to various sites, including the bones, lymph nodes, and less commonly, other organs.
Do Not Miss Diagnoses
- Splenic Infarction with Sepsis: The CT finding of a hypodense area in the spleen suggestive of infarction, combined with possible secondary infection, is critical. Splenic infarction can lead to sepsis, which is life-threatening and requires immediate antibiotic treatment and possibly surgical intervention.
- Bleeding or Rupture of a Colonic Lesion: Although less likely given the current information, any colonic lesion (benign or malignant) could potentially bleed or rupture, leading to severe abdominal pain, hemodynamic instability, and requiring emergency surgery.
Rare Diagnoses
- Systemic Mastocytosis: This rare condition can cause thrombocytosis, abdominal pain, and splenomegaly or splenic infarcts due to mast cell infiltration. However, it would be an unusual diagnosis to make without other supporting evidence like skin lesions or a history of allergic reactions.
- Amyloidosis: Amyloid deposits can cause thickening of the colon wall and systemic symptoms including weight loss and fatigue. However, amyloidosis is rare and would require specific diagnostic tests (e.g., biopsy) to confirm.
Antibiotic Coverage
Given the possibility of infection (suggested by the splenic infarction and secondary infection), broad-spectrum antibiotics covering both aerobic and anaerobic bacteria would be appropriate. A possible choice could be:
- Piperacillin/Tazobactam: This combination provides broad coverage, including against Pseudomonas aeruginosa, and is often used in cases of suspected intra-abdominal infections or sepsis.
- Ceftriaxone plus Metronidazole: This combination offers broad coverage as well, with ceftriaxone covering many Gram-negative and some Gram-positive organisms, and metronidazole adding anaerobic coverage.
The choice of antibiotic should be guided by local resistance patterns, patient allergy history, and specific clinical circumstances.