Renal Colic in Emergency Medicine

Context

Renal colic, which affects between 2-3% of the worlds population, commonly presents to the ED. It may present at any age, although there are certain groups more predisposed. You will often see renal colic patients writhing in agony since the pain is sometimes considered worse than that of childbirth.

Management in the ED focuses on:

• Diagnosing renal colic and eliminating other red flag histories
• Delivering sufficient analgesia to manage pain
• Identifying cases that require invasive intervention, for example an infected/obstructed system, and hospitalising those with pain or complications such as infection
• Determining when it is safe to discharge the patient

Definition

Renal colic is caused by renal calculi (stones) as they pass through the ureter to the bladder.

Renal stones may remain in the kidney or can travel spontaneously through the ureter and into the bladder where they pass out through the urine

The pain, which is caused by ureteric muscle contraction in an attempt to move the stone, is often severe and has been compared to childbirth! The pain is due to ureteric muscle contracting in an attempt to shift the stone.

Stone Composition

Renal stones are composed predominantly (60–80%) of calcium oxalate and / or phosphate. 10–15% are struvite and approximately 1% cystine and 1% uric acid.

Occasionally they are made of xanthine, indinavir and triamterene [1].

Cause

Low urine volume is the most common factor in patients who tend to form stones and is easily remedied by increasing fluid intake sufficient to produce a urine output of 3 litres a day [2].

Usually, a causative factor is not identified. Some authorities advise detailed evaluation after a single stone as recurrence rates are high. This does not appear to be cost effective and is probably best reserved for repeat stone formers.

Predisposition

While renal colic can affect anyone at any age, some groups are more predisposed than others. Predisposition is related to age and gender, as well as to biochemical factors and urinary structural abnormalities.

Learning bite

Investigation for underlying cause is best directed at recurrent stone formers.

Sociological Predisposition

Men are approximately twice as likely to present than women. 30 years of age is peak for men to present with renal colic. Females have a bimodal age distribution with peaks at 35 and 55 years.[1]

The recurrence rate is approximately 50% over a ten year period.[1]

Caucasians have been found to be more commonly affected than either Asian or Black people [2].

A family history of renal colic triples a person’s likelihood of developing it.

Medical Predisposition

We have already identified groups most predisposed to stone formation.

Predisposition can be biochemical or anatomical such as urinary tract structural abnormalities [3].

Biochemical predispostion to stone formation

These include:

• Hypercalciuria
• Hypericosuria
• Hyperoxaluria
• Hypocitraturia
• Cystinuria
• Urease producing organisms
• Urea splitting organisms (proteus, klebsiella, serratia and mycoplasma), which produce struvite stones

Anatomical predispostion to stone formation

Classical presentation

Classically the patient suffering from renal colic has a sudden onset of unilateral loin to groin or renal pain, is writhing in agony or restless, and is nauseated. Pain is classically colicky in nature and radiates to the scrotum and tip of the penis or labia majora.

The pain of renal colic is caused by obstruction of flow in the ureter, leading to increased wall tension in the urinary tract. Prostaglandin synthesis is increased, with the resultant vasodilatation causing a diuresis which further increases pressure. Prostaglandins may also cause smooth muscle spasm in the ureter.

There may be intervals between episodes of pain, so it cannot be assumed that cessation of pain means that the stone has been passed and the episode ended.

Learning bite

• Patients with renal colic that ‘has seemed to resolve’ should be imaged.
• Look out for carcinoma in all age groups and aortic complications in the elderly.

Other presentations

Large stones in the renal pelvis will present with haematuria, infection or decreased renal function rather than acute renal colic. These may be staghorn shaped and usually consist of struvite or cystine.

Pyuria may be evident, but this is usually a result of ureteral irritation rather than a sign of infection.

Imaging must be used in all cases that attend the ED and while blood and urine samples should be taken, the findings are often non-specific.

The differential diagnosis of renal colic includes several red flag conditions listed below. For this reason imaging is essential.

• Pancreatitis
• Appendicitis
• Ovarian pathology and torsion
• Pelvic inflammatory disease
• Pregnancy
• Renal infarct
• Aortic aneurysm
• Cholecystitis
• Renal carcinoma, pyelonephritis
• Incarcerated hernia, e.g. abdominal and lumbar
• Diverticular disease
• Pneumonia

Learning Bite

Pay particular attention to renal carcinoma in all age groups and aortic complications in the elderly

Investigations consist of imaging, haematology, biochemistry and urine samples.

Renal colic may also be diagnosed when, with the increased utilisation of imaging, stones are discovered incidentally in the investigation of abdominal pain not originally attributed to renal colic [4].

Learning Bite

Patients with renal colic that has seemed to resolve should be imaged, to eliminate differential diagnoses

Samples Investigation

Urine Samples

Dipstick urine testing should be carried out in patients with suspected renal colic.

Microscopic haematuria will be present in 90% of cases. In about 10% of cases there is no haematuria present. So if it is not present, a reliable history is sufficient to embark on further investigation.

Pyuria is often present but this is often as a result of ureteral irritation rather than infection.

Blood and Urine Samples

In addition to the dip-stick test, urine should be sent for microscopy and culture if infection is suspected from the history or examination.

Recurrent stone formers should have a 24 hour urine collection for:

• Urine volume
• Calcium
• Oxalate
• Uric acid
• Citrate
• Sodium
• Creatinine

Specific therapy will be indicated if abnormalities are found in the course of this screening, e.g. allopurinol for uric acid stones, and measures required to increase calcium excretion in hypercalcaemia, such as thiazide diuretics.

Blood Samples

A full blood count and electrolyte screen should be taken. Samples will also be required for serum amylase, phosphate, urate, bicarbonate and calcium.

Learning Bite

Intravenous (IV) access should be obtained at the same time as blood samples are taken for fluid, analgesia or antiemetic administration

Imaging Investigations

Plain KUB and abdominal radiography

Abdominal radiography, including the kidney ureter and bladder (KUB) radiograph, is commonly the first step in the work up of abdominal pain (see figures). The KUB shows no evidence of renal tract calcification and following contrast (right) there is prompt excretion through the upper tracts. These are normal films.

However, there are several factors to take into consideration when using this method of imaging:

• Plain abdominal radiography (specified on the request form as a KUB view kidney, ureters, bladder KUB) has a low sensitivity for detecting stones at only 40-50%. It is not sensitive for detecting non-radiopaque calculi or for detecting other causes of ureteric obstruction other than renal stone, which are clearly important in the ED.
• The plain KUB has a specificity of 77% for detecting renal stones. This figure is relatively low due to pelvic calcifications and phleboliths which have a similar appearance. Phleboliths have a central lucency. They are also most common in the pelvis, although gonadal vein phleboliths may cause confusion when assessing the lumbar ureter area on the film.
• Stones containing calcium, such as calcium oxalate and phosphate, are easiest to visualise on plain radiography. Less radiopaque stones such as urate, cystine and magnesium ammonium phosphate are poorly seen. Although 90% of stones are composed of calcium salts, only 59% are visible on abdominal radiographs. Small stones are not well visualised and are easily obscured by bowel gas or faecal material.
• Plain radiography is of definite use following specific treatments such as extracorporeal lithotripsy, and also in the follow up of radio-opaque stones that are being managed conservatively. In such cases a patients return to the ED would merit a KUB.

CT KUB

Unenhanced CT is the imaging modality of choice in renal colic, especially in evaluating cases where the diagnosis may be unclear, for example acute flank pain in the elderly patient. It is rapid, can measure calculi and is able to assess the degree of associated urinary obstruction.

It is recommended that CT should be performed within 24 hours of the onset of symptoms as the renal functions could decline rapidly.[10,12]

The CT KUB shows calculus in the right ureter.

False negative rates of 2-7% are probably due to a small size of stone. Stone size is important given that it relates to spontaneous passage.

Secondary signs such as hydronephrosis, perinephric oedema and stranding, and periureteral oedema are commonly seen. Perinephric stranding appears after 2 hours and is maximal at 8 hours.

Criticism of using CT

Criticism of using CT in evaluating renal colic has centred around radiation exposure. Although this is true, diagnostic yield is greater and may merit the risk.

Low dose CT protocols have been evaluated and appear to maintain diagnostic accuracy. In American studies the cost of CT appears to average out as equivalent to IVU.

Patients with flank pain

Studies have shown that patients with flank pain, upon whom a CT is ordered, have calculi in approximately 70% of cases (47%, however, have a coexistent diagnosis)

Stones not seen on CT

Over 99% of stones are seen on CT, the exceptions are pure matrix stones associated with drugs such as indinavir and related protease inhibitors

Alternate diagnoses

Studies have shown that the majority of alternate diagnoses are detected by CT, especially pyelonephritis, renal mass, adnexal pathology, diverticulitis and appendicitis

Learning bite

CT is rapid, avoids contrast and facilitates alternative diagnostics, especially the red flags.

None of the imaging options are available 24/7 but CT is likely to be the most easily accessible. Most trusts will not do a routine CT KUB overnight but will do it on the weekend during daylight hours.

Ultrasound

Ultrasound has a lower sensitivity (24-77%) when compared to CT (96%). Specificity for both techniques approaches 100%.

Ultrasound is often used as the first line imaging technique in pregnant women and children where radiation is best avoided.

Calculi as small as 0.5 mm can be visualised but sensitivity increases with stone size. Visualisation of ureteral jets within the bladder lumen on ultrasound disappears with obstruction and may indicate the presence of ureteral obstruction. Twinkling artefact on Doppler may aid the diagnosis of smaller stones. Magnetic resonance imaging (MRI) has limited usefulness in detecting calculi.

The ultrasound is showing a renal stone.

POCUS – Point of Care Ultra Sound

Emergency physicians are now gaining experience in the use of bedside ultrasound to detect an abdominal aorta aneurysm (AAA) at the earliest clinical opportunity. It is recommended good practice to exclude AAA in patients aged >60 years in whom renal colic is suspected. If a normal sized aorta is seen on US along its full extent then an aortic aneurysm can be excluded.

Imaging in Pregnancy

Renal colic is no more common in pregnancy. Pregnancy represents some special considerations.

Ultrasound remains the investigation of choice in this group of patients. Although the diagnosis can present problems as hydronephrosis of pregnancy can make diagnosis of associated obstructing calculus difficult.

Endovaginal images can help with visualisation in distal ureteric and ureterovesical stonesIf there is any diagnostic uncertainty and if the risks outweigh the benefits then unenhanced CT may be indicated in later pregnancy. 80% of calculi pass spontaneously, therefore favouring conservative management.

Intravenous Urograms (IVU)

This used to previously be the modality of choice but with the advent of non-contrast low dose IVU is no longer recommended.[13] IVU used to be seen as better than computed tomography (CT)-KUB, in assessing the degree of obstruction and facilitating decisions regarding further management. However, decisions on the ongoing management of renal colic are more often based around stone size and location and CT is superior at assessing these.

Often stones will pass spontaneously. This depends on the size and location of the stone. 90% of small stones of 5mm or less pass spontaneously. On average the spontaneous passage rate of stones of all sizes is approximately:

• 25% in the proximal ureter
• 45% in the mid ureter
• 70% in the distal ureter

Most urologists advise sieving urine to facilitate chemical analysis of retrieved fragments, especially in the case of recurrent stone formers.

Since the majority of renal stones pass spontaneously, management in the ED should be directed to rapid diagnosis and pain relief with referral to urology indicated for developing complications.

Analgesia

Traditionally opioids and non steroidal anti-inflammatory drugs (NSAIDS) have been used in renal colic and both appear to be effective. A Cochrane database review in 2005 analysed 29 trials with a total of over 1,600 participants and although heterogeneity limited pooling of results, and the predominant opiate was pethidine, several conclusions could be drawn [5]:

• Rescue medication requirements are less with NSAIDS
• Lower pain scores are reported with NSAIDS
• Higher rates of adverse effects are seen with opiates
• Ureteric inflammation may be reduced in NSAIDS administration facilitating stone passage

Learning bite

Offer an NSAID by any route as first-line treatment for adults, children and young people with suspected renal colic. If contraindicated then offer intravenous paracetamol to adults, children and young people with suspected renal colic or if NSAIDs are not giving sufficient pain relief. Consider opioids if rescue medication required.

When to Admit a Patient

It is only safe to discharge a patient when pain is under control. Brief ceasing of pain may occur during stone passage, and you must have ruled out differential diagnosis so imaging is always recommended.

It is also only safe to discharge patients if there are no complications such as bilateral blockage, single kidney, anuria or signs of infection. These complications warrant hospital admission.

Discharging a patient

A patient must not be discharged if any of the following complications are suspected:

• Failure of pain control
• Anuria
• A risk of renal failure e.g. a solitary kidney or bilateral obstruction
• Infection: Aggressive therapy and monitoring is required for potentially septic patients who also have ureteric obstruction. The presence of pyrexia mandates urgent full blood count, blood and urine cultures, creatinine and lactate levels should also be obtained. Resuscitation using ‘surviving sepsis’ guidelines in a High Dependency Unit environment is advised. Antibiotic options include gentamicin and co-amoxiclav intravenously.
• Hydronephrosis: The presence of hydronephrosis is an indication for urgent nephrostomy and this is usually performed by a radiologist under fluoroscopic guidance.Patients with stones causing significant ureteric obstruction and pain are treated by stenting pending definitive treatment. Correct insertion is evidenced by x-ray confirmation of the proximal coil in the renal pelvis and distal coil in the bladder. In the 20% of cases where placement fails, then nephrostomy is required. Stents have the potential to cause distressing symptoms and impair quality of life and many urologists are attempting to decrease usage [6].

• Renal failure
• Ureteral stricture
• Urine extravasation
• Perinephric abscess
• Xanthogranulomatous pyelonephritis is an unusual suppurative granulomatous reaction to chronic infection, often in the presence of chronic obstruction from a calculus, stricture or tumor. Surgery is invariably required to completely eradicate the infection and the accompanying calculus and/or obstruction. Kidney-sparing surgery may be undertaken in patients with focal disease.

Discharging a patient

The patient can be discharged if they are pain free and apyrexial. There must be no complications or other factors such as those listed above. It is essential that the correct follow up procedures have been set up and that the patient is made fully aware of the correct advice.

Follow up

Sufficient analgesia must be provided so that the pain can continue to be controlled after discharge

Urology outpatient follow up is organised according to local protocols [2]. However, the following must be carried out:

• Outpatients urology clinic appointment must be set up so that the treatment is continued

• Patient should sieve their urine for stone fragments. These should be kept and taken to the urology clinic

Correct advice

Advise the patient of the following:

• If the pain returns, they are to return to the ED immediately
• To return to the ED immediately if they become unwell or experience fever
• How to use the analgesia
• Drink plenty of fluids, and try to increase urine output to two litres per day

Learning bite

Obstruction and infection in renal colic patients mandate urgent urological referral.

Definitive treatment

It is reassuring to know that >95% of stones <5 mm spontaneously pass within 40 days [11, 13]. Treatment is therefore geared towards aiding spontaneous stone passage with surgical intervention required when stones are impacted.

Extra corporeal shockwave lithotripsy (ESWL) – Proximal non obstructing calculi are treated by extra corporeal shockwave lithotripsy (ESWL). This cannot be used in pregnancy, coagulopathy, uncontrolled hypertension and febrile UTI [7].

Medical Expulsive therapy – A longitudinal cohort study by Resim in 2005, based on the discovery of α1 receptors in the distal ureter, found that α1-blockers decreased the number of ureteral colic episodes and also intensity of pain during spontaneous passage of lower ureteral calculi during follow up [8]. There were several weaknesses in trial design and no firm conclusions can be drawn. A further Cochrane review published in April 2018 [12] concluded that although α1-blockers increased stone clearance they also increased adverse events.

A recent meta analysis has also demonstrated that use of calcium channel blockers can marginally increase stone expulsion as compared with standard therapy but the rate of adverse effects was significant [9]. It is current recommendation to therefore offer α1-blocker therapy to only assist expulsion of stones <10mm in size.

Ureterorenoscopy (URS) – Retrieval with endoscopy is utilised for large stones, multiple stones or stones causing significant obstruction.

Flexible ureteroscopy has emerged as the main treatment for mid and distal ureteric stones. A Cochrane review of current RCTs has shown that during follow up of ureteroscopic retrieval of stones, hospital stay and complications are increased in comparison to ESWL but stone free rate is increased. However, heterogeneity prevented extrapolation to definitive clinical decision making. Innovative YAG laser technology may in future influence this decision [6].

PCNL – Percutaneous Nephrolithotomy/Nephrolithotripsy –
A procedure used for removal of large impacted stones or stones where a trial of ESWL and/or URS have failed.

• Stone disease is relatively uncommon in childhood. It may present with haematuria without flank pain
• Although stones are seen in metabolic conditions such as oxalosis, the majority of stones are calcium based
• Infection must be detected in cases of complete obstruction and if hydronephrosis develops nephrostomy inserted urgently
• IVU has a low sensitivity for detecting stones and does not assist in visualising alternative diagnoses; CT-KUB is the currently preferred method of imaging
• Opiates appear to cause more side effects than NSAIDS, and NSAIDS appear as effective in pain relief as opiates
• Limited pyuria is commonly seen in association with ureteric colic
• 1 in 10 cases renal colic do not have haematuria

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    Renal and ureteric stones: assessment and management [NG118]. 2019. [Accessed 21 Feb 2020].
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