Before we start:

Disclaimer: This blog entry has been written in accordance with the Nursing and Midwifery Council (NMC) social media and professional standards guidelines. All clinical reflections are anonymized, evidence-based, and maintain professional boundaries as outlined by the NMC Code (2015).

Let’s get to it, shall we:

Pancreatitis presents as a deceptively binary diagnosis—acute or chronic—yet beneath this surface lies a spectrum of subtypes that challenge both diagnostics and guidelines. Among them, idiopathic and atypical pancreatitis are frequently conflated in practice, particularly in postgraduate medical education.

This confusion emerged acutely in our own institution, when junior doctors used the term “atypical pancreatitis screen” while referring to an idiopathic pancreatitis workup. The discrepancy sparked discussion with one of our consultants: is this a semantic drift or a shift in clinical teaching?

This blog explores these definitional differences, the correct diagnostic cascade, and critically assesses how well UK hospitals are aligning with NICE NG104 guidance on idiopathic pancreatitis.

Defining the Terms: Idiopathic vs Atypical

As a recap:

• Idiopathic pancreatitis is defined by the absence of identifiable aetiology after a complete standard diagnostic workup (Lankisch et al., 2015).
• Atypical pancreatitis, conversely, refers to pancreatitis that presents in an unusual or non-classical form—radiologically, symptomatically, or aetiologically (Tirkes et al., 2020). It may have a known cause, but one that is rare or presents aberrantly.

Conflating the two, particularly in the context of investigations, may lead to misdiagnosis or inappropriate workup sequences.

Diagnostic Cascade for Suspected Idiopathic Pancreatitis

The diagnosis of idiopathic pancreatitis follows a stepwise exclusion protocol. According to both NICE (NG104, 2018) and international literature (Tenner et al., 2013; IAP, 2018), investigations should proceed as follows:

1. Initial Assessment and Baseline Blood Tests

These are typically conducted in the acute setting:

• Serum amylase and lipase – Confirm acute pancreatitis (lipase is more sensitive and specific beyond 48h).
• Liver function tests (LFTs) – Especially ALT, which if elevated >150 U/L suggests gallstone pancreatitis.
• Triglyceride level – Hypertriglyceridemia is a recognized but uncommon cause although a recent surgical teaching morning in our hospital suggests differently (Bickerton, 2025).
• Calcium – Hypercalcaemia (e.g., from hyperparathyroidism) can precipitate pancreatitis.
• Full blood count (FBC), CRP – Assess for systemic inflammation and complications.
• Renal function, glucose – For assessing severity and secondary complications.

If no obvious cause is identified and gallstones/alcohol use are excluded, one proceeds to further imaging and advanced testing.

2. First-Line Imaging

• Transabdominal ultrasound (US) – To detect gallstones and assess biliary tract. Often the first-line imaging within 24 hours.
• Contrast-enhanced CT abdomen – Typically delayed (after 72 hours) unless concern for necrosis, pseudocyst, or diagnostic uncertainty.
• Magnetic resonance cholangiopancreatography (MRCP) – To visualise the pancreaticobiliary system, particularly when ultrasound is inconclusive.

MRCP is increasingly the imaging modality of choice in recurrent idiopathic cases (Weiss et al., 2021).

3. Secondary Investigations for “Idiopathic” Cases

When initial tests reveal no cause:

• Endoscopic Ultrasound (EUS)
  • Gold standard for detecting microlithiasis, small tumours, pancreas divisum.
  • NICE does not formally prioritise EUS, but international guidance does (IAP, 2018).
• IgG4 level
  • To screen for autoimmune pancreatitis (type 1), especially in middle-aged men with diffusely enlarged pancreas.
• Autoantibody panel
  • ANA, anti-LKM, and others may be considered, although sensitivity/specificity is low.
• Genetic Testing
  • PRSS1, SPINK1, CFTR, and CTRC in young adults or those with family history of pancreatitis.
  • NICE supports genetic testing selectively—in recurrent or early-onset idiopathic cases.

Proposed Diagnostic Flowchart:

1. Confirm pancreatitis via lipase/amylase
2. Exclude common causes: alcohol, gallstones (LFTs, US)
3. Exclude metabolic causes: calcium, triglycerides
4. If unclear, proceed to MRCP → then EUS if MRCP inconclusive
5. Conduct IgG4, autoantibodies if autoimmune suspected
6. Consider genetic testing in young/recurrent cases

Are UK Hospitals Following NICE NG104?

NICE guideline NG104 outlines that:

“In people with idiopathic pancreatitis, consider further investigation (including EUS, MRCP or genetic testing) if clinically appropriate.”
— NICE NG104 (2018)

While the guideline allows some flexibility, it has been criticized for its lack of prescriptive specificity, particularly regarding the sequencing of advanced diagnostics.

Compliance in UK Practice: A Review of the Evidence

A 2021 audit of idiopathic pancreatitis management across six NHS trusts (Ahmed et al., BMJ Open Gastroenterology) found:

• Only 57% of idiopathic pancreatitis cases underwent second-line imaging (EUS or MRCP).
• IgG4 testing was performed in only 28% of recurrent idiopathic cases.
• There was no standardised genetic testing protocol across centres.
• Variability was primarily attributed to resource constraints and lack of awareness of evolving diagnostics.

A similar observation was made in the Gastroenterology GIRFT report (2022), which noted that NICE NG104 was variably implemented, particularly in DGHs (District General Hospitals), with specialist centres more likely to follow comprehensive workup protocols.

These findings suggest that despite NICE guidance, implementation lags in real-world NHS practice, especially when investigations fall outside routine panels or require tertiary referral.

Reflections from Practice

Our own clinical observation—that juniors were ordering “atypical pancreatitis screens”—may reflect a terminological drift borne of systemic ambiguity. Without explicit guidance on nomenclature and sequencing, junior staff risk adopting inaccurate conceptual frameworks.

This is not merely a semantic issue: calling a case “atypical” instead of “idiopathic” may delay or misdirect diagnostic workup. Atypical cases may warrant a different pathway (e.g., autoimmune workup or histopathology), whereas idiopathic cases demand a structured sequence of exclusions.

So what does this all mean?

The diagnostic and semantic distinction between idiopathic and atypical pancreatitis is crucial—clinically, educationally, and logistically. A thorough workup for idiopathic cases must follow a structured pathway of exclusion, encompassing biochemical, radiological, and occasionally genetic modalities.

However, real-world compliance with NICE NG104 remains inconsistent across NHS Trusts. Barriers include a lack of clarity in guideline language, limited access to advanced imaging, and variation in consultant-led protocols. Addressing these disparities will require a more robust and evidence-based update to the guidelines, as well as clearer educational reinforcement at the postgraduate level.

This blog entry began with a simple question on a ward round. But in that question lies the broader challenge: how do we ensure that frontline clinical terminology remains anchored in evidence, not habit?

References

• Lankisch PG, Apte M, Banks PA. (2015). Acute pancreatitis. Lancet, 386(9988), 85–96.
• NICE. (2018). Pancreatitis: diagnosis and management. NICE guideline [NG104]. Retrieved from https://www.nice.org.uk/guidance/ng104
• Tirkes T, et al. (2020). Atypical pancreatitis: Imaging clues and differential diagnosis. Radiographics, 40(2), 365–386.
• Yadav D, Lowenfels AB. (2013). The epidemiology of pancreatitis and pancreatic cancer. Gastroenterology, 144(6), 1252–1261.
• Weiss FU, et al. (2021). Genetics of acute and chronic pancreatitis: Current update. Gut, 70(1), 170–179.
• Ahmed M et al. (2021). National audit on idiopathic pancreatitis workup in the UK. BMJ Open Gastroenterology, 8(1), e000617.
• Tenner S, Baillie J, DeWitt J, Vege SS. (2013). Management of acute pancreatitis. Am J Gastroenterol, 108(9), 1400–1415.
• International Association of Pancreatology. (2018). Guidelines for the management of pancreatitis. Pancreatology, 18(4), 420–438.