Splenic Lesions
| Lesion Type / Size | Recommendation |
|---|---|
| Splenic cyst <2 cm (simple, no internal structure) | No follow-up |
| Splenic cyst ≥2 cm | US or MRI in 6–12 months; if stable → annual × 2 then discontinue |
| Hemangioma (confirmed: hyperechoic on US, T2-bright on MRI) | No follow-up |
| Solid lesion <1 cm, low-risk patient, clearly benign appearance | No follow-up |
| Solid lesion <1 cm, indeterminate | CT/MRI in 3–6 months |
| Solid lesion ≥1 cm or indeterminate | MRI or CEUS for characterization; hematology/oncology referral if suspicious |
| Calcified granuloma (multiple small calcifications) | No follow-up (prior granulomatous disease) |
| Splenomegaly (>13 cm in long axis), incidental | Clinical evaluation; CBC, LFTs; consider hematology referral |
Splenic hemangiomas are the most common benign solid splenic lesion. The classic MRI appearance (T2 very bright, T1 hypointense, peripheral nodular enhancement with fill-in) is analogous to hepatic hemangiomas. Confirmed hemangiomas require no follow-up regardless of size.
Abdominal Lymph Nodes
Short-axis diameter is the standard measurement for abdominal lymph node size:
| Short Axis | Morphology | Recommendation |
|---|---|---|
| <10 mm | Fatty hilum, oval shape (normal morphology) | No follow-up |
| 10–19 mm, no known malignancy | Round, indistinct hilum, or isolated finding | CT in 3 months; if stable → no further follow-up |
| ≥20 mm | Any morphology | PET-CT or tissue sampling; oncology referral |
| Any size, necrotic or hypervascular | Any | PET-CT or biopsy; oncology referral |
| Cluster of ≥3 nodes in one station, OR ≥2 involved stations | Even if each <10 mm | Clinical correlation; consider further evaluation |
| Any size, known malignancy | — | PET-CT or biopsy as clinically indicated |
Why This Matters
The >1 cm short-axis threshold for abdominal lymph node enlargement is a widely applied but imperfect criterion — reactive nodes can be enlarged and malignant nodes can be normal-sized. The cluster rule (≥3 nodes in one station or ≥2 stations) is an important addendum that catches early lymphomatous involvement before individual nodes cross the size threshold. Splenomegaly without a known cause should prompt hematologic evaluation rather than imaging surveillance — it is not an imaging diagnosis to manage with follow-up CT.
Reference
Heller MT, Harisinghani M, Neitlich JD, Yeghiayan P, Berland LL. Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 3: White Paper of the ACR Incidental Findings Committee II on Splenic and Nodal Findings. J Am Coll Radiol. 2013;10(11):833–839.