Is a small smooth notch-like thing felt near the left costal margin in a patient at rest with knees slightly flexed, who can take a deep breath without respiratory distress, likely to be the spleen, suggesting splenomegaly?

Is a Palpable Notch at the Left Costal Margin the Spleen?

Yes, a small smooth notch-like structure palpable near the left costal margin in a patient at rest with knees slightly flexed who takes a deep breath is most likely the spleen, and this finding indicates splenomegaly that warrants further investigation. 1

Understanding Normal vs. Abnormal Findings

The spleen does not normally descend below the left costal margin. 2 When any portion of the spleen becomes palpable on routine abdominal examination, splenomegaly is almost universally present and is generally pathological, warranting investigation. 2

Important Caveat About Palpability

However, there is a critical nuance: a palpable spleen is not necessarily enlarged or pathological in all cases. 3 Studies using radionuclide scanning have demonstrated that approximately 18 of 21 patients (86%) with clinically confirmed palpable spleens measuring ≤13 cm on imaging had no evidence of splenic disease on follow-up. 3 Additionally, research shows that when the spleen tip is just below the costal margin, it may not always be palpable, and conversely, some normal-sized spleens can be palpable. 4

Clinical Examination Technique

Physical examination should include percussion and palpation of the entire spleen with measurement of liver span at the mid-clavicular line. 1 The sensitivity and specificity of detecting splenomegaly by physical examination are 93% and 57%, respectively. 1 While physical examination alone is relatively insensitive, it remains noninvasive, easily repeatable, and requires minimal time and cost. 1

Immediate Next Steps

Imaging Confirmation

Abdominal ultrasound is the first-line imaging modality and should be performed immediately to confirm splenomegaly and measure spleen size. 1 The ultrasound should assess:

• Splenic size and echotexture 1
• Presence of focal lesions 1
• Liver size and appearance 1
• Lymphadenopathy 1

A spleen measuring 11-13 cm indicates mild splenomegaly, while >13 cm indicates clinically significant splenomegaly warranting aggressive workup. 1, 5

Essential Laboratory Testing

The initial laboratory panel must include: 1

• Complete blood count with differential to identify cytopenias, leukocytosis, lymphocytosis, or abnormal cell populations 1
• Peripheral blood smear review to identify blasts, atypical lymphocytes, or other abnormal cells suggestive of leukemia or lymphoma 1
• Comprehensive metabolic panel to assess liver function, as liver disease is one of the three most common causes of splenomegaly in the United States 1, 6

Differential Diagnosis Framework

The most common causes of splenomegaly in the United States are liver disease, malignancy, and infection. 6

Hematologic Malignancies

If lymphoproliferative disorder is suspected based on CBC findings, flow cytometry of peripheral blood for immunophenotyping should be performed immediately. 1 Testing for JAK2, CALR, and MPL mutations is recommended if myeloproliferative neoplasm is suspected, particularly with leukocytosis, thrombocytosis, or unexplained splenomegaly. 1, 5

Portal Hypertension

A platelet count below 100,000/mm³ associated with splenomegaly serves as a surrogate measure of portal hypertension. 1 Cirrhosis with portal hypertension is a common cause of splenomegaly. 7

Infectious Causes

Clinical splenomegaly is present in up to 30% of cases of infective endocarditis, though it is not a reliable sign of splenic complications. 8 Malaria and schistosomiasis are common causes in tropical regions. 7, 6

Critical Pitfalls to Avoid

Do not delay bone marrow evaluation in patients with concerning peripheral blood findings, such as blasts, significant cytopenias, or abnormal cell populations. 1

Do not miss lymphoma-associated hemophagocytic lymphohistiocytosis (HLH), as approximately 40-70% of adult HLH cases are malignancy-associated, particularly with Hodgkin lymphoma, diffuse large B-cell lymphoma, and T-cell lymphomas. 1

Do not assume all palpable spleens are pathological without imaging confirmation, as some normal-sized spleens can be palpable, particularly in thin individuals. 3

When to Refer Immediately

Immediate hematology referral is warranted for: 1

• Peripheral smear showing blasts or abnormal lymphocytes beyond typical reactive changes 1
• Presence of cytopenias 1
• Symptomatic splenomegaly without clear etiology after initial workup 1