Urology
Question 23 of 300
A 45 year old woman presents with a 6 hour history of right sided abdominal pain. She describes the pain as "sharp, stabbing" that occurs in "spasms" and radiates inferiorly. She has vomited once during a painful "spasm". On examination you note that despite intravenous morphine she is unable to keep still on the examination trolley due to pain. Her abdomen is soft and nontender. Her full blood count, urea/electrolytes and liver function tests are normal. What is the most likely diagnosis?
Answer:
The patient has features of renal colic secondary to calculi. Renal or ureteric colic is characterised by an abrupt onset of severe unilateral abdominal pain originating in the loin or flank and radiating to the labia in women or to the groin or testicle in men. The pain typically lasts minutes to hours and occurs in spasms (with intervals of no pain or dull ache). The pain is often accompanied by nausea, vomiting, and haematuria, and is usually described as the most severe pain experienced by the person.Renal Calculi
Urology
Last Updated: 12th February 2021
Urolithiasis is the formation of stones anywhere in the urinary tract (the kidney, ureter, or bladder). Renal or ureteric colic generally describes an acute and severe loin pain caused when a urinary stone moves from the kidney or obstructs the flow of urine through the ureter.
Pathophysiology
Urinary stones form when the urine becomes excessively supersaturated with a mineral, leading to crystal formation. Once crystals are formed, they either pass out with the urine or are retained in the kidney, where they can grow and form stones.
Urinary stones are often asymptomatic but may cause pain when they move or obstruct the flow of urine through the ureter. Obstruction of urinary flow causes an increase in tension in the urinary tract wall. The increasing pressure stimulates the synthesis and release of prostaglandins, and subsequent vasodilatation induces a diuresis which further increases pressure within the kidney. Pain from urinary stones can also be due to smooth muscle spasm (as a result of prostaglandins acting directly on the ureter), hyperperistalsis (due to the obstruction), oedema, and mucosal irritation.
Urinary stones usually obstruct at one of three sites: the vesico-ureteric junction, in the mid-ureter where the ureter crosses the iliac vessels, or the pelvi-ureteric junction.
Types of stones
- Calcium stones
- Calcium stones make up about 80% of urinary stones and may be calcium oxalate stones (80% of cases) or calcium phosphate stones (20% of cases).
- Calcium oxalate stones are associated with low urine volume, hypercalciuria, hyperuricosuria, hyperoxaluria, and hypocitraturia.
- Calcium phosphate stones (hydroxyapatite or brushite) are associated with low urine volume, hypercalciuria, hypocitraturia, high urine pH, and conditions such as primary hyperparathyroidism and renal tubular acidosis.
- Uric acid stones
- Uric acid stones make up about 10–20% of urinary stones and are associated with hyperuricosuria and a low urinary pH (less than 5.5).
- Struvite stones (infection stones)
- Struvite stones make up 1–5% of urinary stones and result from bacterial infection that hydrolyses urea to ammonium and raises urine pH (greater than 7.2). They consist of a mixture of magnesium, ammonium, and phosphate.
- Cystine stones
- Cystine stones make up 1% of urinary stones and result from cystinuria, a genetic disorder that causes cystine to leak through the kidneys and into the urine.
- Drug-induced stones
- Drug-induced stones represent about 1% of all urinary stones. They are formed by crystallised compounds of a drug or due to unfavourable changes in urine composition during drug treatment.
- Drugs that impair urine composition include acetazolamide, allopurinol, aluminium magnesium hydroxide, ascorbic acid, calcium, furosemide, laxatives, vitamin D, and topiramate.
- Drugs that crystallise in urine include allopurinol/oxypurinol, amoxicillin/ampicillin, ceftriaxone, quinolones, ephedrine, indinavir, magnesium trisilicate, sulphonamides, triamterene, and zonisamide.
Risk factors
- Age and gender — the incidence of urinary stones varies by age, with low incidence in children and elderly people. The risk of stone formation is higher in men (aged between 40–60 years of age) than women (3:1 ratio of men to women).
- Ethnicity — urinary stones primarily occur in white people, followed by Hispanics, black people, and Asians.
- Diet — excessive dietary intake of oxalate, urate, sodium, and animal protein are associated with increased stone formation.
- Chronic dehydration — fluid intake is inversely proportional to the risk of stone formation.
- Obesity — the prevalence and incident risk of kidney stones is directly correlated with higher weight and body mass index.
- Environmental factors — high ambient temperatures increase the risk of stone formation due to the impact of temperature on fluid status and urine volume.
- Family history — a positive family history is associated with an increased risk of forming stones.
- Drugs — drug-induced stones represent about 1% of all urinary stones.
- Medical history — certain conditions increase the risk of stone formation. These include
- Anatomical abnormalities of the urinary tract — horseshoe kidney, ureteral stricture, ureteropelvic junction obstruction, ureterocele, caliceal diverticulum, caliceal cyst, or tubular ectasia (medullary sponge kidney), and vesico-uretero-renal reflux.
- Gastrointestinal conditions — jejuno-ileal bypass, intestinal resection, Crohn’s disease, malabsorptive conditions, enteric hyperoxaluria after urinary diversion, and bariatric surgery.
- Genetic conditions — cystinuria, primary hyperoxaluria, renal tubular acidosis, and cystic fibrosis.
- Conditions which alter urinary volume, pH, and/or concentrations of certain ions — hyperparathyroidism, nephrocalcinosis, diabetes, hypertension, polycystic kidney disease, gout, sarcoidosis, spinal cord injury, neurogenic bladder, and increased levels of vitamin D.
Clinical features
- Perform a full history and examination
- Renal or ureteric colic is characterised by an abrupt onset of severe unilateral abdominal pain originating in the loin or flank and radiating to the labia in women or to the groin or testicle in men.
- The pain typically lasts minutes to hours and occurs in spasms (with intervals of no pain or dull ache). The pain is often accompanied by nausea, vomiting, and haematuria, and is usually described as the most severe pain experienced by the person.
- The person may complain of dysuria, urinary frequency, and straining (due to the stone irritating the detrusor muscle when it reaches the vesico-ureteric junction).
- Perform a full and thorough abdominal examination to help exclude differential diagnoses, such as ruptured aortic aneurysm, appendicitis, diverticulitis, and peritonitis.
- The person may be restless and unable to lie still (which helps to differentiate renal colic from peritonitis).
- Consider urine dipstick testing to support the diagnosis and to exclude infection.
- Check for haematuria — the presence of haematuria can support the diagnosis of renal or ureteric colic. However, specificity and positive predictive values are poor, and the absence of haematuria does not exclude a diagnosis but should prompt consideration for other causes of pain.
- Check for nitrite and leucocyte esterase — the presence of nitrite (with or without leucocyte esterase) in the urine suggests a urinary tract infection.
Management
- Diagnostic imaging:
- Arrange urgent (within 24 hours of presentation) imaging to confirm the diagnosis and assess the likelihood of spontaneous stone passage.
- For most adults, offer low-dose non-contrast CT (computed tomography).
- If a woman is pregnant, offer ultrasound instead of CT.
- For children and young people, offer ultrasound first line. Low-dose non-contrast CT may be considered if there is still uncertainty about the diagnosis after an ultrasound scan.
- Arrange urgent (within 24 hours of presentation) imaging to confirm the diagnosis and assess the likelihood of spontaneous stone passage.
- Analgesia:
- Offer a non-steroidal anti-inflammatory drug (NSAID) by any route as first-line treatment for adults, children and young people with suspected renal colic.
- Offer intravenous paracetamol to adults, children and young people with suspected renal colic if NSAIDs are contraindicated or are not giving sufficient pain relief.
- Consider opioids for adults, children and young people with suspected renal colic if both NSAIDs and intravenous paracetamol are contraindicated or are not giving sufficient pain relief.
- Do not offer antispasmodics to adults, children and young people with suspected renal colic.
- Watchful waiting:
- This is considered for asymptomatic renal stones in adults, children, and young people if the stone is:
- Less than 5 mm.
- Larger than 5 mm and the person (or their family or carers, as appropriate) agrees to watchful waiting after an informed discussion of the possible risks and benefits.
- This is considered for asymptomatic renal stones in adults, children, and young people if the stone is:
- Medical expulsive therapy:
- This involves the use of an alpha-blocker to facilitate spontaneous stone passage during the observation period. It is considered for people with distal ureteric stones less than 10 mm.
- Surgical treatment:
- This is offered to adults with ureteric stones and renal colic within 48 hours of diagnosis or readmission if pain is ongoing and not tolerated or the stone is unlikely to pass. The choice of surgical procedure depends on factors such as the size of the stone, the age of the person, any contraindications, whether a previous procedure has failed in the past, and anatomical considerations. Options include:
- Shockwave lithotripsy (SWL) — a non-invasive outpatient treatment that focuses shock waves on the stone to break it up. Stone particles are passed spontaneously.
- Ureteroscopy (URS) — involves the use of various energy sources (such as lasers) to break up the stone.
- Percutaneous nephrolithotomy (PCNL) — a procedure in which a nephroscope is passed percutaneously into the collecting system and the stone is fragmented and extracted through the nephroscope.
- This is offered to adults with ureteric stones and renal colic within 48 hours of diagnosis or readmission if pain is ongoing and not tolerated or the stone is unlikely to pass. The choice of surgical procedure depends on factors such as the size of the stone, the age of the person, any contraindications, whether a previous procedure has failed in the past, and anatomical considerations. Options include:
- Metabolic testing:
- Consider stone analysis for adults with ureteric or renal stones.
- Measure serum calcium for adults with ureteric or renal stones.
- Blood testing (serum calcium) and stone analysis allow the diagnosis of treatable conditions, such as cystinuria, uric acid stones, and primary hyperparathyroidism.
- Consider referring children and young people with ureteric or renal stones to a paediatric nephrologist or paediatric urologist with expertise in this area for assessment and metabolic investigations.
- Give appropriate dietary and lifestyle advice to reduce the risk of recurrence of renal or ureteric stones. Advise the person:
- To increase their fluid intake.
- To add fresh lemon juice to drinking water and avoid carbonated drinks.
- To reduce salt intake.
- That they should not restrict their daily dietary calcium intake.
- To eat a balanced diet, including plenty of fruits and vegetables, and maintain a healthy weight.
Complications
- The main complications of renal and ureteric stones are obstruction of urinary flow and infection.
- Obstruction of urinary flow can decrease the glomerular filtration rate of the affected kidney (and increase renal excretion of the unaffected kidney). Persisting obstruction (for more than 48 hours) can lead to reduced renal blood flow and irreversible kidney damage.
- The obstructed renal unit may become infected, causing obstructive pyelonephritis or pyonephrosis (a build up of high-pressure pus behind the obstruction). If this occurs, the person is at risk of developing life-threatening sepsis.
- Other possible complications include:
- Renal carcinoma
- Chronic kidney disease (CKD)
- Coronary heart disease (CHD)
- Rupture — rarely, spontaneous rupture of a renal calyx with the development of a urinoma (due to urine extravasation) may occur in people with urinary stones
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
