## Distinguishing Interstitial vs. Necrotizing Pancreatitis **Key Point:** The hallmark discriminator between interstitial and necrotizing pancreatitis is the presence or absence of pancreatic necrosis on contrast-enhanced CT imaging. Interstitial pancreatitis shows normal or homogeneous pancreatic enhancement; necrotizing pancreatitis shows areas of non-enhancement (necrosis). ### Imaging Criteria (Revised Atlanta Classification) | Feature | Interstitial Pancreatitis | Necrotizing Pancreatitis | |---------|---------------------------|-------------------------| | **Pancreatic enhancement** | Homogeneous, normal | Heterogeneous with non-enhancing areas | | **Pancreatic necrosis** | Absent | Present (≥30% of pancreas) | | **Peripancreatic fluid** | May be present | Often present | | **Organ failure** | Absent or transient | Often present | | **Mortality** | < 1% | 5–15% | **High-Yield:** The **absence of pancreatic necrosis on contrast-enhanced CT** is the defining feature of interstitial pancreatitis. This is the single best discriminator because it directly addresses the pathological distinction: interstitial edema without tissue death vs. actual pancreatic parenchymal necrosis. **Clinical Pearl:** Dynamic contrast-enhanced CT (arterial and portal venous phases) is essential. Failure of a pancreatic region to enhance in the arterial phase indicates necrosis. Delayed imaging (> 5 days) may be needed if early CT is equivocal. **Mnemonic:** **PANE** — Pancreatic necrosis Absent = interstitial; Pancreatic necrosis Evident = necrotizing. ### Why Laboratory Values Don't Discriminate Serum amylase, CRP, and other biomarkers correlate with severity and systemic inflammation but **do not reliably distinguish morphological type**. Both interstitial and necrotizing pancreatitis can present with markedly elevated amylase and high CRP. The distinction requires imaging. [cite:Harrison 21e Ch 346]
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