Sickle Cell Disease with Acute Vaso-Occlusive Crisis
The most likely diagnosis is sickle cell disease (Option C) presenting with an acute vaso-occlusive crisis affecting the right upper quadrant, triggered by the preceding upper respiratory tract infection. 1
Clinical Reasoning
The constellation of findings definitively points to sickle cell disease:
- Normochromic normocytic anemia (Hb 72 g/L) with elevated reticulocyte count (7.2%) indicates active hemolysis with compensatory bone marrow response 1
- Target cells and red cell inclusion bodies on peripheral smear are characteristic morphologic features of sickle cell disease 2, 3
- Acute right upper quadrant pain following URI represents a classic vaso-occlusive crisis precipitated by infection, one of the most common triggers 1
- Fever (38.9°C) and tachycardia (110/min) are consistent with both the precipitating infection and the acute crisis itself 1
- Normal bowel sounds and absence of rebound tenderness argue against surgical emergencies like appendicitis or bowel infarction 1
Why Other Options Are Incorrect
GI infarction (Option A) would typically present with peritoneal signs, absent bowel sounds, and more severe hemodynamic instability, none of which are present here 4. The peripheral smear findings of target cells and inclusion bodies are not characteristic of mesenteric ischemia.
Lead poisoning (Option B) can cause basophilic stippling (a type of inclusion body), but would not explain the acute presentation following URI, the degree of hemolytic anemia with 7.2% reticulocytosis, or the target cells 3. Lead toxicity presents with chronic exposure history and different clinical features.
Acute appendicitis (Option D) is excluded by the right upper quadrant (not right lower quadrant) location of pain, absence of rebound tenderness, and the hematologic findings that clearly indicate a hemoglobinopathy 1.
Key Diagnostic Features of Sickle Cell Crisis
The peripheral smear findings are pathognomonic:
- Target cells are consistently present in sickle cell disease due to altered red cell membrane properties 2
- Red cell inclusion bodies (likely Howell-Jolly bodies from functional asplenia) are common in sickle cell patients 3
- Normocytic anemia with elevated reticulocytes reflects the chronic hemolytic state with marrow compensation 1
Clinical Context Supporting the Diagnosis
Infection as a precipitant: Upper respiratory infections are well-established triggers for vaso-occlusive crises in sickle cell disease, causing sickling through hypoxemia, dehydration, and inflammatory mediators 1. The temporal relationship between URI and abdominal pain is classic.
Right upper quadrant involvement: Hepatic sequestration or hepatic infarction commonly occurs in sickle cell crises, presenting as right upper quadrant pain without peritoneal signs 1. The liver is a frequent site of vaso-occlusion.
Hemodynamic stability with tachycardia: The vital signs show compensated physiology typical of acute pain crisis rather than surgical catastrophe 1. Blood pressure remains normal despite tachycardia, which reflects pain and fever rather than shock.
Common Pitfall to Avoid
Do not mistake sickle cell crisis for a surgical abdomen simply because of acute abdominal pain 5. The absence of peritoneal signs, presence of characteristic hematologic findings, and clinical context of recent infection should redirect evaluation toward medical management of vaso-occlusive crisis rather than surgical exploration 1. The peripheral smear is diagnostic and should always be carefully reviewed in patients presenting with anemia and abdominal pain 5.