Section 1: Epidemiology and aetiology
Renal colic, resulting from the passage of stones, is a common cause of morbidity. Treatment aimed at prevention of recurrence can be effective and should be an opportunity to address lifestyle factors.
Renal stones are common, with a lifetime prevalence of about 10% in industrialised nations. They are about twice as common in men, although they may be increasing in women. Those of European or Middle Eastern descent appear to have an increased risk.
Stones form in the renal tubules and collecting system when a supersaturation threshold is reached for the constituent concerned. This depends on a number of factors, including its urinary concentration, the urinary pH and citrate concentration. Most stones are calcium based and the rate of recurrence is as high as 50% at 10 years (see table 1).
|TABLE 1: TYPES AND FREQUENCY OF RENAL STONE|
|Type of renal stone||Frequency|
|Calcium oxalate/mixed calcium||80%|
|Magnesium ammonium phosphate (struvite), uric acid||5-10%|
There is an increased incidence of stones in people with metabolic syndrome. In this population, stones are more likely than average to be uric acid in nature, although calcium stones are still the most common.
Renal stone colic is pain caused by the attempted passage of stones along the urinary tract. The classic waxing and waning character is a result of the peristaltic contraction of the ureter. Although variable, it can be extremely painful. The most common sites for stones lodging are the pelvico-ureteric junction (PUJ) and vesico-ureteric junction (VUJ).
Eighty per cent of patients with renal stones form calcium stones, most of which are composed primarily of calcium oxalate or, less often, calcium phosphate. The other main types include uric acid, struvite (magnesium ammonium phosphate) and cystine stones. The same patient may have more than one type of stone concurrently.
Section 2: Making the diagnosis
Renal stones are often asymptomatic. Incidental stones are identified in about 5% of patients by abdominal ultrasonography or CT imaging.
Renal colic classically presents as sudden onset, severe flank pain, which may be intermittent. It often radiates to the groin, such that pain in the testicle, penile tip, labia or clitoris may be described.
The severity may cause tachycardia, sweating, nausea and vomiting or even collapse. A patient with renal colic will be rolling around or pacing the floor, in contrast to a patient with peritonitis, who will lie completely still.
Other presentations of renal stones include the painless passage of grit, stones or visible blood, dysuria, urgency or less typical flank or abdominal pains.
Dipstick haematuria is common and supports the diagnosis, but is not a universal finding.
To secure a diagnosis of renal colic, imaging is required, because the differential diagnoses include a range of vascular, urological, intestinal, upper GI and gynaecological causes of severe abdominal pain.
The current gold standard first-line imaging for acute flank pain is a non-contrast CT scan (NCCT). This has near 100% sensitivity, even for small stones, and will usually demonstrate urinary obstruction if present. In the absence of stones, it may demonstrate an alternative significant diagnosis.
IV urogram (IVU) has fallen out of favour because numerous trials have shown inferior sensitivity and specificity to NCCT, with the potential toxicity of a contrast load. It does, however, give better demonstration of obstruction if present.
A plain kidneys, ureters, bladder (KUB) X-ray may be helpful in known radio-opaque stone formers with a classic presentation.
Ultrasound scanning (USS) is safe, inexpensive and good at demonstrating stones >5mm in the renal calyces, PUJ and VUJ. It is limited by its ability to detect ureteric stones.
USS may be useful in pregnant patients, or ruling out specific differentials such as gallstones, abdominal aortic aneurysm and ovarian cyst pathology. It is good for detecting hydronephrosis.
The following basic investigations are useful in cases of renal colic:
- FBC - a raised WCC may signify infection, although WCC up to 16x109/L is often seen in acute renal colic
- Bone profile (to include calcium and phosphate)
- Serum urate
- Urine microscopy, culture and sensitivity
The patient should also be advised to sieve their urine and collect any stone/sediment for analysis.
Section 3: Managing the condition
In suspected renal colic, initial management can be carried out at home if these criteria are met:
- No signs of infection (negative dipstick for leucocytes/nitrites, afebrile, systemically well).
- Low risk of renal failure (no chronic kidney disease, single functioning kidney or renal transplant; unilateral symptoms; passing good volumes of urine).
- Good initial response to symptomatic measures.
- Symptom control with oral medication (analgesia, antiemetics).
- Ability to maintain sufficient fluid intake.
- Ideally less than 60 years of age (ensure telephone contact and adequate social support in place).
- Pregnancy excluded in women of childbearing age.
- No diagnostic uncertainty regarding serious alternative diagnoses (for example, leaking abdominal aortic aneurysm).
If these criteria are met, fast-track referral to hospital for diagnostic imaging (NCCT for a first presentation) should be within seven days. If not, the patient should be referred to hospital for emergency urological evaluation.
For most patients, the best initial analgesia is rectal diclofenac (50-100mg). Alternatively, for initial control, the parenteral route may be used (diclofenac 75mg IM).
If there are contraindications to NSAIDs (renal impairment, upper GI disease, volume depletion, ACE inhibitors), opiates may be used, although they are usually not as effective and may worsen the nausea. Consider diamorphine 1.25-2.5mg IV or 2.5mg subcutaneously. Pethidine is generally avoided.
Maintenance can often be achieved with a combination of:
- Diclofenac 25-50mg three times a day oral/rectal
- Paracetamol 1g four times a day oral/rectal
- Codeine 30-60mg every six hours
Nausea and vomiting are common; initial parenteral options include IM or oral cyclizine, prochlorperazine or metoclopramide.
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Conservative management with observation and reassessment is reasonable in the absence of infection, hydronephrosis and unmanageable symptoms if the stone is <10mm.
Medical expulsive therapy uses pharmacological smooth muscle relaxation to aid stone passage.
For 5-10mm stones, this may increase the passage rate by 30%. With smaller stones, it may reduce transit time and symptoms. The best evidence is for alpha-blockers (tamsulosin 400 microgram once a day).
Infection in an obstructed system is an emergency, as it can destroy nephrons and progress to septic shock. Management involves broad-spectrum IV antibiotics and decompression with nephrostomy or stent.
Ureteric stone removal is indicated for stones >15mm, smaller stones that are failing to progress, persistent obstruction or unmanagable symptoms. The most common techniques are extracorporeal shock wave lithotripsy and ureteroscopy with laser lithotripsy.
Measures applicable to all stone formers include:
- Maintain fluid intake to excrete >2.5L per day and drink before going to bed, to induce nocturia
- Restrict sodium intake to reduce urinary calcium and increase bicarbonate
- Cut animal protein intake
- Maintain a healthy weight
Section 4: Prognosis
Most stone formers have no genetic, anatomical or tubular defect predisposing them to stones. They have calcium-containing stones, often in the context of modifiable metabolic and lifestyle factors.
Recurrent stones are common and can cause significant morbidity, including progressive renal failure.
A large registry analysis including >3m adults from North America showed that even a single kidney stone episode was associated with a significant increase in the likelihood of chronic kidney disease, including end-stage renal failure.1 Therefore, in patients with renal stones, control of cardiovascular risk factors and modification of lifestyle are essential.
Recurrent stone formers (especially those adhering to the measures above) should be assessed in a specialist clinic.
Prevention of renal stones
A recent systematic review including 28 RCTs showed that increased fluid intake substantially reduced the risk for recurrent calcium stones.2
In men with high soft-drink consumption, decreasing intake also reduced recurrent stone risk. Results were mixed for the potential benefit of other dietary interventions.
In those with multiple past calcium stones, adjunctive treatment with thiazides, citrate and/or allopurinol further reduced the risk for stone recurrence. Baseline biochemistry did not predict efficacy of any treatment, apart from uric acid levels.
Section 5: Case study
A 46-year-old male calls his out-of-hours GP with a six-hour history of sudden onset, severe left loin pain.
When the doctor arrives, the patient is on his knees, grasping his loin. He has vomited and reports urinary urgency and frequency.
He has recently been diagnosed with type 2 diabetes and takes metformin, simvastatin and bisoprolol. His says his father had kidney stones, although there is no personal history. His job involves a lot of time driving and working in air-conditioned offices. He drinks two cups of tea and one or two cans of soft drink a day.
He is overweight (BMI 31). His pulse is 94bpm, BP 150/95mmHg and temperature 36.4 degsC. Abdominal examination is unremarkable. Urine dipstick shows blood 2+ and leucocytes 1+, and is sent for microscopy, culture and sensitivity.
A working diagnosis of renal colic is made, and 10mg morphine IM plus 75mg rectal diclofenac administered, with immediate relief. He is prescribed co-codamol and diclofenac and advised to sieve his urine.
Next day, the pain has subsided. The patient is sent for a plain KUB X-ray, which shows a 7mm radio-opaque density in the left VUJ. He is given a prescription for tamsulosin 400 microgram once a day.
Five days later the patient attends for follow-up. His pain has gone and he presents a small, irregular brown stone, which is sent for analysis. His MSU showed no growth. Bloods are requested for FBC, U&Es, calcium, phosphate and urate.
During the consultation he is asked about dietary habits and admits to eating a lot of meat products and fast food. He is advised that he has a 50% chance of forming another stone within 10 years, and that preventive measures should include cutting down on meat and salt, but most importantly, maintaining a high urine output.
Section 6: Evidence base
- Alexander RT, Hemmelgarn BR, Wiebe N et al. Kidney stones and kidney function loss: a cohort study. BMJ 2012; 345: e5287.
- Fink HA, Wilt TJ, Eidman KE et al. Medical management to prevent recurrent nephrolithiasis in adults: a systematic review for an American College of Physicians Clinical Guideline. Ann Intern Med 2013; 158: 535-43.
- The British Association of Urological Surgeons. Stone guidelines. 2012. www.baus.org.uk/AboutBAUS/publications/stones-guidelines
- Clinical Knowledge Summaries. Renal colic - acute. 2009. www.cks.nhs.uk/renal_colic_acute
- Turk C, Knoll T, Petrik A et al. European Association of Urology. Guidelines on urolithiasis. 2013. www.uroweb.org/gls/pdf/21_Urolithiasis_LR.pdf
- By Dr Matt Varrier, specialist registrar in renal medicine, Ms Susan Willis, specialist registrar in urology, and Dr Marlies Ostermann, consultant in renal medicine and critical care, Guy's & St Thomas' NHS Foundation Trust, London.
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1. Alexander RT, Hemmelgarn BR, Wiebe N et al. Kidney stones and kidney function loss: a cohort study. BMJ 2012; 345: e5287.
2. Fink HA, Wilt TJ, Eidman KE et al. Medical management to prevent recurrent nephrolithiasis in adults: a systematic review for an American College of Physicians Clinical Guideline. Ann Intern Med 2013; 158: 535-43.