Analgesia and imaging in suspected stone

01Principles and purposeThe professional or clinical skill and the decisions it supports.

Effective analgesia makes assessment more humane and often improves the patient’s ability to cooperate with imaging. It does not need to await a scan. Start with the actual medicines already taken, including over-the-counter tablets and combination products, because the apparent first hospital dose may not be the first dose of the day. Record allergy phenotype, weight, renal function, volume status and relevant ulcer or cardiovascular history before choosing the drug and route.

NICE NG118 places an NSAID ahead of intravenous paracetamol and reserves consideration of an opioid for inadequate relief or contraindications to both earlier approaches. This is a decision sequence rather than a requirement to expose every patient to each drug. A patient with previous NSAID-induced gastrointestinal bleeding should move to the appropriate alternative. If a correctly administered NSAID has provided insufficient relief, adding the next suitable option is preferable to repeatedly increasing an unsafe drug burden.

EAU 2026 also prioritises an appropriate NSAID but describes opioids or ketamine as a second choice. Do not merge these into an invented common hierarchy: the UK worked decisions here use the NICE sequence. Similarly, EAU describes initial ultrasound with noncontrast CT confirmation in acute flank pain, whereas NICE directly recommends urgent low-dose noncontrast CT for adult suspected renal colic. The leading clinical question and the applicable population must remain visible.

Imaging should answer why the patient has pain and whether renal drainage is safe. Noncontrast CT measures stone burden and location and can reveal alternative pathology; contrast may be needed for a different diagnostic question or selected anatomical planning. Ultrasound avoids radiation but may miss ureteric stones, so a negative study must be interpreted with the symptoms and risk. Pregnancy and childhood require their own next-step discussion rather than an adult CT or drug dose copied without review.

Key points

In the NICE sequence, use an appropriate NSAID first, intravenous paracetamol if an NSAID is contraindicated or insufficient, and an opioid if both earlier choices are unsuitable or inadequate; antispasmodics are not recommended.
For adult suspected colic, NICE specifies low-dose noncontrast CT within twenty four hours; pregnancy uses ultrasound instead, and children under sixteen start with urgent ultrasound.
Prescribe intravenous paracetamol in both milligrams and millilitres and count all other paracetamol; weight at or below fifty kilograms changes the dose and daily ceiling.
An NSAID-first recommendation does not remove renal, gastrointestinal, cardiovascular, hypersensitivity or pregnancy exclusions for the selected product.
Renal-colic analgesia and imaging proceed together; neither a previous stone history nor response to a drug establishes the cause of pain.
Persistent intolerable pain or an unlikely-to-pass ureteric stone triggers the NICE forty-eight-hour treatment recommendation; infection or threatened renal drainage can require more urgent action.

02Situations and prioritiesThe context, relevant information and actions that matter most.

Reconcile earlier medicines

Ask for names, strengths, timing and amount of analgesics already used. Specifically identify combined cold or codeine preparations containing paracetamol and any ibuprofen, naproxen or diclofenac. The cumulative exposure determines what can safely be administered now.

Identify NSAID hazards

Previous NSAID-triggered wheeze or swelling, ulcer bleeding, established arterial disease or significant heart failure can exclude diclofenac. Renal failure is a product contraindication; acute kidney injury, dehydration or interacting nephrotoxic medicines requires a different initial risk assessment even before a numeric threshold is considered.

Define paracetamol dosing weight

Use measured weight rather than appearance or an assumed adult dose. A forty-eight-kilogram adult needs a weight-based dose, while an adult over fifty kilograms with dehydration, malnutrition, chronic alcohol use or hepatocellular impairment has a lower daily ceiling than an otherwise low-risk adult.

Assess the response and diagnostic fit

Document pain and function after treatment: the ability to lie still, drink and mobilise is useful alongside a pain score. Persistent guarding, a changing pain site, hypotension or fever requires diagnostic reassessment. Opioid-associated drowsiness can make the patient quieter without representing improvement in the underlying obstruction.

Red flags requiring action

Uncontrolled pain despite appropriate medicines needs urgent urological reassessment for drainage or stone treatment.
Sedation, falling respiratory rate or oxygenation after an opioid requires immediate assessment and withholding further opioid doses.

03Assessment and interpretationHow to gather information, assess the situation and recognise uncertainty.

Reasoning sequence

Consider the information, its meaning and its limitations before deciding what follows.

01
Adult low-dose noncontrast CT
Why
Identify the stone and assess a cause of pain requiring a different intervention.
Interpretation and limitations
For suspected renal colic in adults, arrange the NICE examination within twenty four hours. Discuss an alternative protocol with radiology if the leading concern is vascular, inflammatory or another non-stone diagnosis. Do not add contrast phases routinely merely because pain is severe.
02
Pregnancy or paediatric ultrasound
Why
Begin with the population-specific NICE radiation-sparing examination.
Interpretation and limitations
Pregnancy calls for ultrasound instead of routine CT. Children and young people under sixteen should receive ultrasound within twenty four hours; persistent diagnostic uncertainty can justify low-dose noncontrast CT after discussion. In pregnancy, ultrasound, MRI and selected low-dose CT have distinct specialist roles, rather than an automatic second scan for everyone.
03
Renal function liver risk and urine testing
Why
Check factors that change drug handling or the urgency of the urinary presentation.
Interpretation and limitations
Use creatinine and a relevant renal estimate alongside baseline values and volume status. Obtain liver tests when hepatic disease or toxicity risk makes them relevant, and review the whole paracetamol exposure. Urine testing assesses haematuria and possible infection but cannot by itself settle either diagnosis.
04
Reassessment after treatment
Why
Determine whether analgesia has enabled safe observation or exposed a need for escalation.
Interpretation and limitations
Repeat observations and pain assessment after each intervention. After morphine, assess consciousness, respiratory rate, oxygenation and blood pressure while maintaining access to resuscitation. Persistent severe pain despite the appropriate sequence requires a source or stone-treatment decision, not a requirement to reach a maximum opioid dose.

04Worked approachesCases with ordered reasoning, an action and a check of the outcome.

01Worked caseCalculate a low-weight paracetamol doseA forty eight kilogram adult woman has suspected colic and a previous NSAID-associated bleeding ulcer.

1She is not pregnant, has normal renal and hepatic function, no dehydration or alcohol risk, and has taken no paracetamol that day. The bleeding history excludes diclofenac. Her pain score is seven out of ten and repeated vomiting makes an oral initial regimen unreliable, so intravenous paracetamol is selected without a trial of another NSAID.
2Using Paracetamol ALTAN 10 mg/ml, the prescribed dose is 15 mg/kg: 48 multiplied by 15 equals 720 mg, corresponding to 72 ml. It is infused over fifteen minutes. Her weight-based daily ceiling is 60 mg/kg, or 2,880 mg from every source, which remains below the product’s 3 g ceiling for this weight group; further doses must be at least four hours apart.
3Pain falls to two out of ten and vomiting settles, so no opioid is required. Low-dose noncontrast CT that day identifies a three millimetre distal ureteric stone without concerning obstruction. Examination and the scan identify no alternative emergency, and she subsequently retains oral fluid.
4After clinician review, she leaves with a reconciled oral analgesia plan and scheduled stone follow-up, understanding that the intravenous dose counts towards the same day’s total. She recovers the stone five days later; follow-up confirms symptom resolution and stable renal function. The record includes both the successful dose calculation and the observed clinical outcome.

02Inadequate reliefUse monitored rescue without losing the diagnosisAn eligible adult remains in severe pain after appropriate earlier analgesic treatment.

1Confirm that the earlier drug was delivered at the intended dose and that enough time has passed to assess its effect. Recheck observations, examination and the scan request. Under the NICE sequence, an opioid becomes an option when the NSAID and intravenous paracetamol are contraindicated or provide insufficient relief.
2For a monitored adult without the selected formulation’s contraindications, a prescriber may choose morphine 2.5 mg intravenously as a low initial dose, given slowly over four to five minutes with the patient recumbent. Assess breathing, alertness, blood pressure and pain before any further individually prescribed dose; do not infer a recurring schedule from that single administration.
3If pain remains intolerable, involve urology to consider urgent decompression or stone removal. The goal is adequate relief with a safe source plan, not escalating sedation. Once the acute indication has resolved, stop rescue opioid use rather than converting it into an open-ended repeat prescription.

03Uncertain imagingChoose the next diagnostic question explicitlyInitial findings do not adequately explain the symptoms or the risk remains concerning.

1A negative ultrasound cannot exclude every ureteric stone. In a child with persisting uncertainty, consider low-dose noncontrast CT under the NICE pathway. For pregnancy, obtain obstetric and radiological advice on further investigation, balancing the likelihood of obstruction or an alternative emergency against imaging risks.
2If an adult has hypotension, peritoneal signs or a vascular concern, choose imaging for that suspected condition rather than repeatedly pursuing a stone-only examination. Normal urine testing and temporary analgesic response should not override examination evidence of another diagnosis.
3Communicate the final imaging interpretation, analgesic response and unresolved uncertainty to the receiving team or follow-up service. State who will review a pending report and what findings would trigger immediate recall, so that a successful scan acquisition is not mistaken for a completed diagnostic process.

05Relevant medicines and safetySpecific regimens and precautions when the skill involves prescribing.

An actionable NSAID option when the person and route are suitable; the IV postoperative indication is not being transferred to stone colic.

Voltarol 75 mg/3 ml intramuscular diclofenac

An adult renal-colic dose is one 75 mg deep intragluteal injection. If necessary the renal-colic schedule permits one further ampoule after thirty minutes; the combined daily diclofenac maximum is 150 mg and ampoule treatment must not exceed two days.

Do not administer for renal or hepatic failure, active/recurrent ulcer or bleeding, prior NSAID-related gastrointestinal bleeding, established ischaemic/cerebrovascular or peripheral arterial disease, or NYHA II–IV heart failure. Exclude NSAID-triggered respiratory or allergic reactions and product/metabisulphite hypersensitivity. Avoid duplicate NSAIDs; assess anticoagulants, steroids, SSRIs, methotrexate, lithium and ACE inhibitor/diuretic renal interactions. Use additional caution in frailty, low weight and volume depletion. Stop for bleeding, rash or organ deterioration. Ampoules are not recommended in children; pregnancy requires a separate decision, with fetal renal/ductal risk from twenty weeks and third-trimester contraindication. Never give this product as an intravenous bolus. The selected Voltarol label states that it should not be administered during breastfeeding.

The NICE next analgesic option when an NSAID is unsuitable or has not provided sufficient relief, using a selected weight-based formulation.

Paracetamol ALTAN 10 mg/ml intravenous infusion

For both adult weight bands below, infuse each dose over at least fifteen minutes, leave at least four hours between doses and give no more than four doses in twenty four hours. Above 50 kg without hepatotoxicity risk, give 1 g as 100 ml per dose, maximum 4 g/day. At more than 33 kg up to and including 50 kg, give 15 mg/kg as 1.5 ml/kg per dose, maximum 60 mg/kg/day capped at 3 g; apply the renal interval and hepatic-risk limits in the cautions.

At creatinine clearance 30 ml/min or less, separate doses by at least six hours. Above 50 kg with hepatocellular impairment, chronic alcohol use, malnutrition or dehydration, the daily maximum is 3 g; severe hepatocellular insufficiency or paracetamol/propacetamol/product hypersensitivity excludes treatment. Count every oral, rectal and IV paracetamol source and prescribe both mg and ml. Review probenecid, which reduces clearance, and anticoagulant monitoring during continued use; flucloxacillin and glutathione-depletion states increase pyroglutamic-acidosis risk. Use the smaller of applicable weight/risk limits and switch to an appropriate oral regimen when feasible. This adult example does not supply neonatal or paediatric dosing.

An opioid rescue example after the NICE earlier analgesic options are unsuitable or inadequate; a single-dose example does not authorise a standing infusion or daily maximum.

Hameln morphine sulfate 10 mg/ml injection

For the selected monitored adult rescue situation, prescribe 2.5 mg intravenously once, injected over four to five minutes with the patient recumbent. This lies within the product’s 2.5–10 mg adult starting range; reassess before any further individual prescription and stop as the acute need resolves.

The selected product excludes respiratory depression/insufficiency, obstructive airways disease, renal or liver failure, hypovolaemic hypotension, ileus and relevant hypersensitivity. Its additional exclusions include ureteral stenosis, prostatic hypertrophy, pancreatitis/gall-bladder dysfunction, inflammatory bowel disease, cerebral trauma or raised intracranial pressure, coma, convulsive disorders, acute alcoholism, myxoedema and phaeochromocytoma. Do not combine with an MAOI or within fourteen days of stopping one. In lesser renal/hepatic impairment, frailty or older age use specialist dose reduction and monitoring. Benzodiazepines, alcohol and other sedatives increase respiratory risk. Monitor respiration, consciousness, oxygenation and blood pressure with resuscitation available; withhold for toxicity. Pregnancy requires a separate specialist benefit–risk decision. Breastfeeding use is not recommended by this selected morphine label; this formulation is not recommended below twelve years.

06Feedback, follow-up and evidenceReview outcomes, seek feedback and identify what to improve.

Record the cumulative NSAID and paracetamol exposures and the remaining permitted doses, including the effect of changing from intravenous to oral treatment.
After an opioid, observe breathing, level of consciousness and circulation; a low pain score in a newly somnolent patient is not a satisfactory endpoint.
Reassess renal function when dehydration, continued obstruction or nephrotoxic co-medication creates an accumulation or kidney-injury risk.
Before discharge, verify manageable symptoms, oral tolerance, a reviewed imaging result and a clear escalation/follow-up plan rather than relying on medication administration alone.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Exactly fifty kilograms belongs to the lower band

The ALTAN table uses more than fifty kilograms for the standard 1 g adult band. A person weighing exactly fifty kilograms remains in the 15 mg/kg group, with a 750 mg dose and maximum 3 g/day before other relevant risk reductions.

Route does not remove systemic NSAID harm

Intramuscular administration bypasses swallowing, not gastrointestinal bleeding, cardiovascular risk or renal prostaglandin effects. Previous NSAID-related bleeding is still an exclusion, and concurrent oral NSAID use still contributes to the risk assessment.

Different guidelines can answer the same question differently

NICE and EAU both support timely imaging and effective analgesia but organise the initial steps differently. A named guideline in an examination stem matters; use its actual sequence without implying that a distinct international recommendation does not exist.

Analgesia failure is a management signal

Repeated pain despite appropriate medication can justify intervention. Assess whether the stone can realistically pass and whether obstruction persists; there is no requirement to exhaust every rescue drug before discussing source treatment with urology.

08Common pitfallsFrequent interpretation and management errors.

01
Giving the entire 100 ml paracetamol container to a low-weight adult confuses packaging with the prescribed dose and may exceed the weight-based regimen.
02
Transferring an intravenous diclofenac postoperative schedule or bolus technique into renal colic bypasses the selected route and safety instructions.
03
Adding an antispasmodic because the word colic implies spasm conflicts with the NICE recommendation and does not substitute for appropriate analgesia.
04
Interpreting a quiet sedated patient as successfully treated can miss opioid toxicity or continuing obstruction, so document physiology and meaningful function.

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