Reasoning GP · Algorithm · 1-page summary
Incidental renal mass
For: adults with a renal mass or cyst found on imaging done for another reason, and GP aftercare after kidney cancer treatment. Not for: children with an abdominal mass (block 2; abdominal mass algorithm); choosing, stopping or changing anticancer treatment (oncology team).
Core rule: a solid enhancing or indeterminate mass, or a Bosniak III–IV cyst, needs prompt urology/uro-oncology referral per the local pathway — an imaging finding is not itself an NG12 criterion, so never wait for haematuria. Close the loop on every incidental finding: a named team and booked imaging.
0Stop — call 999 now — emergency admission
- Known or suspected angiomyolipoma + sudden severe flank or abdominal pain, pallor, faintness or shock — acute haemorrhage (Wunderlich) → 999 emergency admission.
- Adjusted calcium >3.5 mmol/L, or hypercalcaemia at any level with confusion, AKI or persistent vomiting → 999
- While waiting: no imaging or blood tests in primary care first.
1Triage by the radiology report — Bosniak v2019
| Lesion | Action |
|---|---|
| Solid enhancing or indeterminate | Possible RCC → Urgent prompt urology/uro-oncology (MDT); suspected cancer pathway if the local pathway says so. |
| Bosniak III–IV cyst | III indeterminate, IV likely malignant → Urgent uro-oncology MDT. |
| Bosniak IIF | Secondary-care active surveillance → urology ≤2 weeks for a surveillance plan. |
| Macroscopic fat (AML) | Benign → specialist surveillance plan, outside the cancer pathway. |
| Bosniak I–II | Benign → no follow-up; document it. |
2Screen — one row is enough
- Unexplained visible haematuria aged ≥45, or persisting or recurring after a treated UTI → Suspected cancer pathway (NG12).
- New bilateral leg oedema (IVC tumour thrombus) or severe symptoms → Same-day hospital. Renal vein/IVC involvement on imaging or suspected metastases → Urgent specialist.
- Bone pain + hypercalcaemia (metastatic RCC?) → Urgent urology/uro-oncology; calcium 3.0–3.5 → Same-day assessment. Myeloma suspected → local haematology pathway.
- New hypertension + hypokalaemia, or adrenal-looking lesion → endocrinology via the adrenal incidentaloma pathway (metanephrines, aldosterone–renin ratio, 1 mg dexamethasone test).
- Child with a palpable abdominal mass, enlarged organ or unexplained visible haematuria → consider very urgent referral ≤48 h (NG12); Same-day if unwell. Do not palpate repeatedly.
- After treatment: new neurological symptoms or spinal pain suggesting metastases → Same-day acute oncology/MSCC pathway (NG234). On immunotherapy, new diarrhoea, breathlessness, jaundice, confusion, hypotension or polyuria → Same-day oncology.
3Assess
☐ Report: solid/cystic, enhancement, fat, Bosniak ☐ Haematuria, flank pain, weight loss, smoking, family history ☐ Flank mass, BP, left varicocoele, leg oedema ☐ Urinalysis (non-visible = 1+ or more); FBC, U&E/eGFR, calcium; LFTs if indicated; ACR if eGFR <60 or proteinuria
Not in primary care: urine cytology, renal biopsy, routine bone scan. Ultrasound cannot assign Bosniak → specialist CT or MRI.
4Classify — specialist-led; GP acts on the category
- Solid enhancing mass (single, bilateral or multifocal) = RCC vs oncocytoma vs lipid-poor AML. NG256: <2 cm consider active surveillance; ≥2 cm surgery, or surveillance/ablation if unsuitable or declined.
- Fat on CT = angiomyolipoma, benign; with tuberous sclerosis → specialist TSC centre.
- Uncertain or indeterminate → treat as solid enhancing; never leave unfollowed.
5Treat today — reduce risk, protect the kidneys
- Smoking cessation → NHS Stop Smoking Service; weight management (NG246); BP control.
- Kidneys: avoid unnecessary or prolonged NSAIDs; an eGFR check must not delay cancer imaging.
- After nephrectomy: creatinine/eGFR; eGFR <60 → offer ACR and manage per CKD guidance; ACE inhibitor/ARB only where indicated (albuminuria).
- On TKI or immunotherapy: follow the oncology plan; treat BP by standard principles; never change anticancer therapy or start steroids without oncology. Doses: NICE/SPC, BNF, local formulary.
6Refer routinely — after blocks 0–2
- Age ≤46, multiple tumours, 1st/2nd-degree relative with renal cancer, syndromic features → clinical genetics + urology (NG256). Suspected HLRCC: no biopsy.
- AML painful, previous bleed (now stable), high-risk vascular features or growth → urology ≤2 weeks. No repeat ultrasound without a specialist plan.
7Never reassure by — close the loop on every incidental finding
- “Probably a cyst” on ultrasound — it cannot assign a Bosniak category.
- No haematuria and a well patient — most RCC are now found incidentally.
- Not meeting NG12 — a solid enhancing mass still needs prompt referral.
- “Benign AML” with sudden flank pain and faintness — a bleed is 999.
- A surveillance plan nobody booked — confirm scan dates and the named team.
- A growing lesion or new enhancement on surveillance — prompt referral.
8Safety-net — say it, then document it
999 “Call 999 for sudden severe pain in your side or tummy with feeling faint or collapse.” Same-day “On immunotherapy, new diarrhoea, breathlessness or yellow skin — or new weakness, numbness or bladder or bowel problems — contact the oncology team today.” Same week “Contact us or your urology team this week for blood in your urine, new pain or a lump in your side, or weight loss you cannot explain.”
✓Safe to leave primary care only if — all five, documented
No block 0–2 feature
Lesion categorised by specialist imaging
Referral sent per local pathway, or Bosniak I–II recorded
Named team and imaging dates on record
Hereditary criteria checked; safety-net given
Summary of the full Reasoning GP incidental renal mass algorithm, which holds the detail and evidence. Sources: NICE NG256 Kidney cancer (March 2026); NICE NG12 Suspected cancer (updated April 2026); NICE NG234; NICE NG246; Bosniak classification v2019; EAU RCC guideline; NICE TA780, TA830, TA964. The local urology/uro-oncology referral pathway takes precedence. Clinical reference — follow local referral and prescribing policies and check doses: NICE/SPC, BNF.