Raised Creatinine or Falling eGFR Algorithm

Safety

Red flags — potassium, overload, obstruction and the unstable patient

Done

Hyperkalaemia Potassium ≥6.5 mmol/L, or hyperkalaemic ECG changes at any potassium (peaked T waves, broad QRS, sine wave), or symptoms (palpitations, weakness, syncope) → 999. Potassium 6.0–6.4 mmol/L with AKI or acute illness → same-day hospital assessment and an ECG. Potassium 5.5–5.9 → think pseudohyperkalaemia (haemolysed or delayed sample, high platelets or white cells), review drugs and repeat promptly (UK Kidney Association 2023).

Sepsis with a rising creatinine Suspected infection with high-risk features (new confusion, systolic BP ≤90 mmHg, heart rate >130, respiratory rate ≥25, SpO₂ <92% on air, mottled skin, no urine in 18 hours) → 999 (NICE NG253).

Pulmonary oedema or uraemia Breathless at rest, crackles, falling saturations; or drowsiness, confusion, asterixis, pericardial rub → 999. Giving fluid to an overloaded patient causes pulmonary oedema.

Anuria or obstruction with infection No urine output with deterioration → 999. Palpable bladder or retention → catheterise and same-day assessment. Fever, loin pain and a rising creatinine with suspected obstruction (pyonephrosis) → 999 — ultrasound within 6 hours in hospital.

AKI stage 2–3 Creatinine ≥2× baseline, or ≥354 µmol/L with an acute rise, or oliguria (<0.5 mL/kg/h for 6 hours or more) → same-day hospital assessment; 999 if physiologically unstable. NICE NG148 asks for nephrology discussion within 24 hours for stage 3.

Blood + protein on dipstick with AKI Possible rapidly progressive glomerulonephritis or vasculitis (rash, haemoptysis, joint pains, sinus symptoms, hypertension) → same-day nephrology discussion (NICE NG148).

Myeloma with complications Renal impairment with hypercalcaemia (calcium >3.0 mmol/L or symptomatic), suspected spinal cord compression or AKI → same-day. Stable suspected myeloma → myeloma blood tests (below; within 48 hours if hypercalcaemia or leukopenia) and suspected cancer pathway referral if they suggest it (NICE NG12).

A raised creatinine is a lab result, but the first question is whether the patient is in danger today. Hyperkalaemia, pulmonary oedema, uraemia, an obstructed infected kidney and sepsis kill within hours, so they are screened before any thought about chronicity. The potassium thresholds follow the UK Kidney Association 2023 guideline used on the site's AKI protocol: 6.5 mmol/L or above, or ECG change, is a 999 call; 6.0–6.4 in an acutely unwell patient needs same-day hospital assessment. Dipstick blood and protein in a patient with AKI is the signature of glomerulonephritis — NICE NG148 asks for urgent nephrology discussion, because days matter in rapidly progressive disease.

Diagnose

Is it AKI or CKD? — compare with the baseline

Done

Find the baseline

Look back through old results. The best reference is a recent stable pre-illness creatinine, or a representative stable value from the previous 7–365 days. Stage on creatinine, not eGFR — eGFR lags when creatinine is changing. If there is no baseline, treat it as possible AKI until proven otherwise and repeat.

AKI — NICE NG148 / KDIGO

Any one of: creatinine rise ≥26 µmol/L within 48 hours; rise ≥50% within 7 days; urine output <0.5 mL/kg/h for more than 6 hours. Stage 1: 1.5–1.9× baseline (or ≥26 µmol/L in 48 h). Stage 2: 2.0–2.9×. Stage 3: ≥3×, or ≥354 µmol/L with an acute rise, or renal replacement therapy.

AKI alerts

The NHS England AKI algorithm flags results automatically to the practice — act on every alert the same day by phoning or reviewing the patient.

CKD — NICE NG203

eGFR <60 mL/min/1.73 m² for more than 3 months, or markers of kidney damage (ACR >3 mg/mmol, haematuria of renal origin, structural abnormality) for more than 3 months. Stage by eGFR (G1–G5) and ACR (A1–A3).

New low eGFR, patient well

No baseline and no AKI features → repeat U&E within 2 weeks to exclude AKI (NICE NG203), then confirm chronicity at 3 months. Avoid red meat for 12 hours before the test.

Things that move creatinine

Cooked meat or creatine supplements, heavy exercise, high muscle mass (overestimates), low muscle mass in frail or amputee patients (creatinine looks falsely reassuring), trimethoprim and cimetidine (block secretion, small rise without true fall in GFR), pregnancy (creatinine normally falls).

Acute on chronic

A step change on top of known CKD is AKI on CKD until proven otherwise — stage it against the CKD baseline, not against "normal".

The one decision that changes everything is acute versus chronic. AKI is defined by change from the patient's own baseline, so the old results are the most useful test you have. eGFR is calculated on the assumption that creatinine is stable, which is why it under-reports a rapidly evolving AKI and why NICE stages on creatinine. A new low eGFR in a well patient with no previous result is repeated within 2 weeks — partly to catch an AKI, partly because a single eGFR can be distorted by a steak supper or a gym session. Only after 3 months of persistence is it CKD.

Diagnose

History — the cause is usually in the story

Done

Pre-renal (fluid and perfusion)

Vomiting, diarrhoea, poor intake, heat, sepsis, bleeding, heart failure, recent new antihypertensive or diuretic. Postural dizziness, thirst, reduced urine output.

Drugs (ask about every one)

NSAIDs (including over the counter), ACE inhibitor/ARB, diuretics, SGLT2 inhibitor, metformin (not nephrotoxic but accumulates — lactic acidosis), lithium, trimethoprim, aminoglycosides, PPIs (interstitial nephritis), recent iodinated contrast. The "triple whammy" — NSAID + ACEi/ARB + diuretic.

Post-renal (obstruction)

Hesitancy, poor stream, retention, overflow, constipation in older adults, known prostate or pelvic cancer, renal colic, single kidney.

Intrinsic renal

Rash, joint pains, haemoptysis, sinusitis, ear symptoms (vasculitis); recent sore throat; frothy urine or oedema (nephrotic); visible haematuria.

Myeloma clues

Age over 60, bone or back pain, unexplained fracture, fatigue, anaemia, recurrent infections, hypercalcaemia symptoms (thirst, constipation, confusion), weight loss.

CKD risk factors

Diabetes, hypertension, cardiovascular disease, previous AKI, family history of kidney disease, recurrent UTI or reflux, gout, structural renal disease, long-term lithium or calcineurin inhibitors.

Symptoms of advanced disease

Itch, nausea, poor appetite, fatigue, breathlessness, ankle swelling, nocturia, restless legs.

Most community AKI is pre-renal and drug-related: an older person with a dehydrating illness who keeps taking an ACE inhibitor, a diuretic and an over-the-counter NSAID. The history sorts the problem into pre-renal, intrinsic and post-renal, which is the framework that directs both treatment and urgency. Asking about obstruction matters in older men and in constipated frail adults. Myeloma deserves a deliberate question in anyone over 60 with renal impairment and anaemia, bone pain or high calcium, because it is easily missed and kidney damage from light chains is partly reversible if treated early.

Diagnose

Examination and investigations

Done

Observations

BP (lying and standing), pulse, respiratory rate, temperature, SpO₂, mental state; weight. Volume status: mucous membranes, JVP, capillary refill, oedema, crackles.

Abdomen

Palpable bladder, renal masses, PR if retention or constipation suspected. Rash or purpura. Fundi if severe hypertension.

Urine

Dipstick for blood, protein, leucocytes and nitrites before any catheter; ACR; MSU if infection is possible. Record urine output if unwell.

Bloods

U&E (repeat by severity, often within 24–48 hours in AKI stage 1), bicarbonate, FBC, CRP, bone profile, glucose/HbA1c, LFTs. Look at previous creatinine trend.

Myeloma screen (NICE NG12)

Aged 60 or over with persistent bone pain (especially back) or unexplained fracture → offer FBC, calcium, ESR or plasma viscosity, serum protein electrophoresis and serum free light chains. Aged 60 or over with hypercalcaemia or leukopenia and a picture consistent with myeloma → the same tests very urgently (within 48 hours). Also consider them in unexplained renal impairment with anaemia or raised ESR. Urine Bence-Jones only if free light chains are not available.

Vasculitis/GN screen

If blood and protein on dipstick with a rising creatinine: ANCA, anti-GBM, ANA, complement, immunoglobulins — but discuss with nephrology the same day rather than wait for results.

Renal ultrasound

AKI with suspected obstruction or no clear cause → within 24 hours (within 6 hours if pyonephrosis suspected; usually via hospital). CKD: accelerated progression, visible or persistent non-visible haematuria, obstructive symptoms, family history of polycystic kidney disease (aged over 20), eGFR <30, or before biopsy (NICE NG203).

ECG

If potassium ≥6.0 mmol/L, or if potassium cannot be obtained quickly in an unwell patient.

KFRE (CKD only)

In confirmed CKD G3–G5, calculate the 4-variable Kidney Failure Risk Equation (age, sex, eGFR, ACR). Do not use it during an AKI.

Examination is mainly about volume: dry patients need fluid, overloaded patients need the opposite, and the treatment decision depends on getting it right. The urine dipstick done before catheterisation is one of the most valuable tests in AKI, because blood and protein point to an intrinsic renal cause. Ultrasound is targeted — it finds obstruction, the most reversible cause, and gives kidney size (small kidneys suggest chronic disease). The myeloma screen uses serum protein electrophoresis and free light chains; a standard dipstick does not detect light chains. The KFRE is a CKD tool; it is meaningless while creatinine is changing.

Diagnose

Differential — pre-renal, intrinsic, post-renal, chronic

Done

Pre-renal (commonest)

Dehydration, sepsis, bleeding, heart failure or low cardiac output, cirrhosis, over-diuresis, ACEi/ARB in volume depletion. Urea often disproportionately high. Improves quickly with fluid and drug review.

Drug-induced

NSAIDs, ACEi/ARB with diuretic, lithium toxicity, aminoglycosides, contrast, acute interstitial nephritis (PPIs, antibiotics — may have rash, eosinophilia, white cells in urine).

Post-renal

Prostatic obstruction, urinary retention (anticholinergics, constipation, opioids), bilateral stones, pelvic or bladder cancer, blocked catheter.

Intrinsic — Do not miss

Vasculitis / rapidly progressive GN — blood + protein on dipstick, systemic features. Myeloma cast nephropathy — older, anaemia, high calcium, high ESR. Rhabdomyolysis — long lie, high CK, dark urine. Haemolytic uraemic syndrome — bloody diarrhoea, low platelets.

Chronic kidney disease

Stable or slowly falling eGFR over months to years, small kidneys, diabetes or hypertension, anaemia, high phosphate. Confirmed after 3 months.

Spurious

Creatine supplements, meat meal, trimethoprim, high muscle mass — stable, explained, cystatin C can help if doubt (NICE NG203).

Uncertain

Repeat U&E promptly, review drugs, dipstick and ultrasound; seek renal advice and guidance. Albuminuria without a falling eGFR: see the proteinuria algorithm.

The pre-renal, intrinsic and post-renal framework is old but still the most useful way to make sure nothing dangerous is missed. In primary care, pre-renal and drug causes dominate and recover quickly once the precipitant is reversed; that recovery itself confirms the diagnosis. The intrinsic causes are rare but time-critical: vasculitis, myeloma and rhabdomyolysis can each destroy kidney function within days. Cystatin C is useful when muscle mass makes creatinine misleading — NICE NG203 suggests it at initial diagnosis to confirm or rule out CKD where eGFR creatinine may be less accurate.

Refer

Who to refer, how fast

Done

999

Potassium ≥6.5 mmol/L or ECG changes · sepsis with high-risk features · pulmonary oedema · uraemic encephalopathy or pericarditis · anuria with deterioration · pyonephrosis with systemic illness.

Same-day hospital

AKI stage 2–3 · potassium 6.0–6.4 mmol/L with AKI · AKI with no clear cause or unable to drink · oliguria · urinary retention with AKI · AKI with blood + protein on dipstick (same-day nephrology discussion) · myeloma with hypercalcaemia or suspected cord compression · AKI in pregnancy, after transplant or in CKD G4–G5.

Suspected cancer pathway

Protein electrophoresis or free light chains suggesting myeloma → haematology (NICE NG12). Visible haematuria aged 45 or over, unexplained → urology.

Community management

Usually AKI stage 1 only: well, clear reversible cause, able to drink, no oliguria, potassium not significantly raised. Recheck U&E within 24–48 hours and until recovered.

Nephrology (routine/advice) — NICE NG203

5-year KFRE risk >5% · ACR ≥70 mg/mmol (unless due to diabetes and appropriately treated) · ACR ≥30 with haematuria · sustained fall in eGFR of ≥25% with a change in G category, or ≥15 mL/min/1.73 m² within 12 months · hypertension uncontrolled on 4 or more drugs · known or suspected rare or genetic cause · suspected renal artery stenosis. eGFR <30 not known to nephrology is a referral trigger commonly used locally; it is not an NG203 criterion.

Urology

Obstruction needing specialist management, chronic retention.

Very few people with AKI should stay at home: community management is a clinical judgement usually limited to stage 1 with a clear, reversible cause in a patient who can drink and be reviewed again within a couple of days. The CKD referral criteria come from NICE NG203; the important change in that guideline was moving from an eGFR cut-off to the KFRE, so a stable older person with eGFR 28 and a low KFRE can stay in primary care, while a younger person with heavy albuminuria and a KFRE over 5% needs a renal opinion even at a higher eGFR.

Treat

Management at this consultation

Done

AKI or acute illness — sick-day drug review

Stop NSAIDs; hold the sick-day medicines

Stop NSAIDs. Temporarily withhold ACEi/ARB, diuretics, SGLT2 inhibitor and metformin (and consider sulfonylureas for hypoglycaemia risk) during the AKI or dehydrating illness, reviewing each one individually — stopping a diuretic in heart failure can cause overload. Write down when to restart (usually 24–48 hours after eating and drinking normally, with a repeat U&E). Review renally cleared drugs: lithium, DOACs, gabapentinoids, opioids, nitrofurantoin, trimethoprim.

Pre-renal AKI stage 1, managed at home

Oral fluids and treat the cause

Encourage oral fluid if volume deplete and not overloaded (unless fluid-restricted); treat infection (dose antibiotics to renal function; avoid trimethoprim and nitrofurantoin when eGFR is low — check the SPC and local formulary); anti-emetic if vomiting. Recheck U&E within 24–48 hours.

Retention or obstruction

Catheterise; same-day review

Palpable bladder or confirmed retention → urethral catheter (record residual volume); relieve constipation; stop anticholinergics. Watch for post-obstructive diuresis — usually needs hospital.

Potassium 5.5–5.9 mmol/L, patient well

Repeat and review drugs

Repeat promptly on a fresh, quickly processed sample; review ACEi/ARB, spironolactone, trimethoprim, potassium supplements and salt substitutes; low-potassium dietary advice. See the hyperkalaemia algorithm.

Confirmed CKD (after 3 months)

Start the CKD bundle

ACEi/ARB where ACR criteria are met (titrate to maximum tolerated; U&E 1–2 weeks after each change), SGLT2 inhibitor where eligible (NICE TA1075/TA942), atorvastatin 20 mg (NICE NG238), BP target, code CKD. Usual adult dose and eligibility: see the CKD protocol and the SPC.

Suspected myeloma, stable

Myeloma screen

Serum protein electrophoresis, free light chains, FBC, calcium, ESR/PV (within 48 hours if hypercalcaemia or leukopenia); avoid NSAIDs and keep well hydrated.

Do NOT

Stop a heart-failure diuretic blindly; give fluid to an overloaded patient; restart ACEi/ARB without a repeat U&E; label CKD on one eGFR; use the KFRE during AKI.

Document

Stage, baseline used, cause, drugs held and the restart plan, repeat test date, who will act on the result.

Next steps: see Acute kidney injury · Chronic kidney disease · Sick day rules

The single most effective intervention in community AKI is the drug review: stop NSAIDs and pause the medicines that worsen kidney perfusion or accumulate when the kidneys fail. Think Kidneys and the site's sick-day rules protocol present this as individualised advice rather than a blanket rule, because stopping a diuretic in heart failure or an SGLT2 inhibitor without a plan can both cause harm. The restart plan matters as much as the stop — many patients are never restarted on renoprotective drugs after an AKI. For confirmed CKD the first consultation is about starting the kidney-protecting bundle; the detail, monitoring and second-line choices are on the CKD protocol.

Lifestyle

Self-care and prevention

Done

Sick-day advice Selected patients (CKD, diabetes, heart failure, older adults on the sick-day medicines) get written advice on pausing drugs during vomiting, diarrhoea or fever with poor intake, and when to restart.

Avoid NSAIDs Including over-the-counter ibuprofen and topical-to-oral switches; tell the pharmacist about kidney disease.

Fluids Drink normally to thirst; extra in hot weather or illness unless fluid-restricted for heart failure or advanced CKD.

Supplements Avoid creatine supplements before blood tests; herbal remedies can harm kidneys. Use salt substitutes only with advice (potassium).

Cardiovascular risk Stop smoking, less salt, healthy weight, activity — CKD is mainly a cardiovascular risk state.

Know your numbers Encourage people to know their eGFR, ACR and BP target, and to mention kidney disease before contrast scans or new medicines.

Most AKI in the community is preventable. Sick-day guidance targeted at the right patients, avoiding NSAIDs, and remembering that dehydration plus an ACE inhibitor plus a diuretic is a classic recipe for AKI will prevent the next episode. For people whose results confirm CKD, the lifestyle measures are the same as for cardiovascular prevention, because people with CKD are far more likely to die of cardiovascular disease than to reach dialysis.

Safety

Follow-up and safety-netting

Done

Repeat bloods

AKI stage 1 at home: U&E within 24–48 hours and until back to baseline. New low eGFR, well: repeat within 2 weeks, then at 3 months to confirm chronicity.

Restart plan

Recheck U&E before or soon after restarting held drugs; restart ACEi/ARB once recovered rather than leaving them off.

After AKI

Review at 3 months (U&E, ACR, BP) — AKI raises the risk of CKD, cardiovascular events and death (NICE QS76). Code the AKI episode.

Results to chase

Myeloma screen, ultrasound, ACR, autoantibodies — named clinician responsible.

Remote consultations

Telephone, video or online consultation with any 999 feature → convert to a 999 call, not a later appointment; if examination is needed to decide, see the patient the same day.

SCA safety-net wording

"Your kidney blood test has changed and we need to recheck it on [date]. Stop the ibuprofen and the [tablets] until then. If you are passing much less urine, can't keep fluids down, feel very drowsy or confused, or become short of breath, contact us the same day or call 111. If you collapse, have chest pain or severe breathlessness, or your heart is racing, call 999."

Audit checklist

Baseline found · stage recorded · potassium checked · drugs held with restart date · dipstick before catheter · repeat U&E booked · 3-month review coded.

AKI is a risk marker, not a one-off event; NICE QS76 expects a review within 3 months, and that review is the GP's job. The safety-net covers the features of worsening AKI — falling urine output, inability to drink, drowsiness, breathlessness — and the palpitations or collapse of hyperkalaemia. The commonest failure is administrative: a repeat test that no one chases, or a held ACE inhibitor that is never restarted.