QuestionSBA
QuestionChoice
This is a large stone with radiological evidence of obstruction and hydronephrosis in the context of a single kidney. Therefore, it would be inappropriate to manage this expectantly since the stone is unlikely to be spontaneously passed and more urgent treatment is required due to susceptibility to acute kidney injury, long-term sequelae for his solitary kidney and risk of urosepsis.
52933
b
Expectant management with regular diclofenac
QuestionChoice
Haemofiltration may be required if this patient presents with certain features of severe kidney injury, such as treatment-resistant fluid overload, hyperkalaemia, acidosis or uraemia. This patient is at risk of acute kidney injury and may require filtration further down the line if the obstruction is not rapidly relieved. There is no indication that this is an issue at present, with his blood tests within normal parameters.
52934
c
Urgent haemofiltration
QuestionChoice
This would be the treatment of choice for removal of stones less than 20 mm in size. This breaks the stone up and allows the patient to pass the pieces through the urine. This is not the best approach in acute obstructions with hydronephrosis and would not be appropriate for this patient where the stone is 30 mm in size.
52935
d
Extracorporeal shock lithotripsy
QuestionChoice
There is radiographic evidence of renal obstruction with an associated large stone in the context of a single kidney. This patient is at significant risk of deterioration from sepsis due to the obstruction. Prompt action is also required due to the presence of a single kidney to protect his long-term kidney health but also due to the absence of a second kidney to compensate in terms of providing adequate renal function in the acute setting. In the first instance, decompression with a nephrostomy is required. The stone is likely to require subsequent surgical removal due to its large size (> 10 mm).
52932
a
Percutaneous nephrostomy
QuestionChoice
Since this patient has only one kidney, they are at risk of end-stage renal disease and may, eventually, require a renal transplant. Kidney transplants are reserved for patients with established end-stage renal failure (which this patient does not have). It can take several years for an appropriate donor match to be identified, so it is not an acute form of renal replacement therapy; if this patient went on to sustain a severe acute kidney injury, haemofiltration may be required. If they did not recover from the acute injury, then they would need long-term dialysis as a bridge to transplant.
52936
e
Renal transplant
Concept
Chapter
"# Summary

Urolithiasis refers to stones that may form anywhere in the urinary tract (usually in the kidneys). They are often asymptomatic but may cause pain +/- obstruction of the flow of urine. Stones usually form due to supersaturation of urine, with the main types including calcium oxalate, calcium phosphate, uric acid, struvite and cystine stones. A common presentation is with renal or ureteric colic, where there is severe spasmodic pain that classically moves from loin to groin. Other symptoms include nausea, vomiting and haematuria; patients who develop an infected obstructed urinary system may be systemically unwell and febrile. Investigations include a urine dip and culture, blood tests for renal function and inflammation markers and a non-contrast CT KUB. Ultrasound is an alternative for young people and pregnant women. Management depends on how likely stones are to pass spontaneously based on location and size as well as symptom severity, presence of complications (e.g. infection, obstruction) and the patient's background. Options include watchful waiting with analgesia, medical expulsive therapy, percutaneous nephrolithotomy, ureteroscopy, shock wave lithotripsy, or (rarely) open surgery. Thought should be given to whether an underlying condition (such as hyperparathyroidism) may be driving stone formation and patients should be advised on how to reduce the risk of recurrence. Preventative medical treatment may be indicated in some cases of recurrent stones.

# Definition

Urolithiasis refers to urinary calculi (stones) anywhere in the urinary tract. They form due to supersaturation of urine causing crystal formation, which then aggregate into larger stones.
 
# Epidemiology
 
- Urinary tract stones are common, with a lifetime prevalence of 12% in men and 7% in women
- Peak incidence is between 35-45 years of age
- Modifiable risk factors include:
    - Obesity
    - Chronic dehydration
    - High ambient temperatures
    - Diet high in oxalate, urate, sodium and animal protein
- Non-modifiable risk factors include:
    - White ethnicity
    - Family history of stone formation
    - Structurally abnormal renal tract (e.g. vesicoureteric reflux, horseshoe kidney)
    - Comorbidities including diabetes, gout, hyperparathyroidism, Crohn's disease, cystinuria 
 
# Aetiology

- **Calcium oxalate stones**
    - Majority (approximately 70%) of stones
    - Radiopaque
    - Can form in any urine pH
    - Associated with low urine volume and hypercalciuria
- **Calcium phosphate stones**
    - Approximately 10% of stones
    - Radiopaque
    - Tend to form in alkaline urine
    - Associated with renal tubular acidosis types 1 and 3
    - Associated with primary hyperparathyroidism
- **Uric acid stones**
    - Approximately 10% of stones
    - Radiolucent
    - Only form in acidic urine (pH < 5.5)
    - Associated with diabetes, obesity and gout
    - May occur due to malignancy (due to high cell turnover, especially due to chemotherapy)
- **Struvite stones**
    - Approximately 5% of stones
    - Radiopaque
    - Composed of magnesium, ammonium and phosphate
    - Often occur due to urease-producing bacterial infection (e.g. Proteus, Enterobacter, Klebsiella)
    - Associated with alkaline urine
    - May form staghorn calculi (which involve the renal pelvis and extend into mulitple calyces)
- **Cystine stones**
    - 1% of stones
    - Faintly radiopaque
    - Occur due to cystinuria (an autosomal recessive condition affecting renal reabsorption of amino acids)
    - More likely to form in alkaline urine
    - Often occur in young patients
- **Medication-induced stones**
    - 1% of stones
    - Occur due to crystallisation of medications or their compounds
    - e.g. indinavid, ceftriaxone, allopurinol, zonisamide
 
# Signs and Symptoms
 
- Stones are often asymptomatic, especially if small, and may be detected incidentally on imaging
- The classic presentation is with renal or ureteric colic
        - There is severe, spasmodic pain that often starts in one flank (or ""loin"")
        - It may then radiate to the groin (i.e. ""loin to groin"" pain)
        - It may also radiate to the scrotum, labia or anterior thigh
        - Onset is usually sudden
        - Patients may be restless and pace or writhe around due to severe pain
- Renal angle tenderness may be present on examination
- Visible haematuria (or may be microscopic and detected on dipstick only)
- Dysuria, urinary frequency and having to strain to pass urine may occur (due to detrusor muscle irritation)
- Nausea and vomiting
- Fever, diaphoresis, rigors and hypotension may be present if there is concurrent infection
- There may be urinary hesitancy or an intermittent stream if there is obstruction
 
# Differential Diagnosis
 
- **Pyelonephritis** presents with fever, flank pain, nausea and vomiting and urinary symptoms such as frequency, urgency and dysuria - it may complicate obstruction due to urinary stones but often occurs in the absence of stones (often due to an ascending lower urinary tract infection)
- **Appendicitis** presents with periumbilical pain migrating to the right lower quadrant (rather than flank pain), nausea, vomiting and fever are common and patients may have classic examination findings (e.g. maximal tenderness at McBurney's point, Rovsing's sign)
- **Diverticulitis** presents with intermittent left lower quadrant pain and tenderness, fever is common as well as altered bowel habit (often with the passage of blood and/or mucus) 
- **Ovarian torsion** presents with acute severe pelvic or lower abdominal pain (which may be intermittent and radiate to the flank), nausea and vomiting; there may be a palpable mass on examination
- **Ectopic pregnancy** presents with lower abdominal or pelvic pain and vaginal bleeding, often in women with a history of a recent missed period; if there is tubal rupture patients may develop vomiting, tachycardia, hypotension and shock 
- **Rupture or dissection of an abdominal aortic aneurysm** may mimic renal colic, especially in older men presenting with flank and groin pain and haemodynamic instability

# Investigations

**Bedside:**

- **Urinalysis** for haematuria; nitrites and leukocytes may be present in infection (leucocytes may also be present in urine due to ureteral irritation) - urine pH may also guide the likely cause of stones
- **Urine MC&S** looking for any bacteria that may be causing a complicating infection or struvite stones
- **24 hour urine collection** in recurrent stone formers to assess urine volume, calcium, oxalate, uric acid, citrate, sodium and creatinine

**Bloods:**

- **Full blood count** may show raised white cell count due to infection
- **U&Es** may show deranged renal function e.g. if there is obstruction
- **CRP** which may be significantly raised in infection
- **Bone profile** looking for hypercalcaemia
- **Serum urate** if raised may increase suspicion of uric acid stones
- **Venous blood gas** may show acidosis and low bicarbonate if there is underlying renal tubular acidosis; lactate may be raised in patients systemically unwell with infection
- **Coagulation screen** to check for a bleeding diathesis prior to intervention 
- **Blood cultures** in patients with suspected infection

**Imaging:**
 
- **Non-contrast CT KUB** should be done urgently in patients with suspected renal colic
- **Ultrasound KUB** is an alternative that should be offered to pregnant women and under 16 year olds
- **Abdominal X-ray** also has a role e.g. to follow up radio-opaque stones that are being managed conservatively

**Special tests:**

- **Stone analysis** to identify their composition and guide prophylactic management - sieving urine may be advised to retrieve fragments especially if there is recurrent stone formation
 
# Management 
 
**Conservative:**

- Patients should be educated on urinary tract stones and safety-netted regarding risks (e.g. infection, obstruction)
- As stones often pass spontaneously, watchful waiting may be appropriate for asymptomatic stones < 5mm with no complications (this may also be trialled in larger stones if patients have been counselled regarding risks and benefits)
- Dietary and lifestyle advice should be provided on how to reduce recurrence risk
    - Drink 2.5-3 litres of water per day
    - Avoid carbonated drinks (may acidify urine)
    - Add fresh lemon juice to water (contains citrate which reduces stone formation)
    - Eat a balanced diet and maintain a healthy weight
    - Reduce salt intake
    - Do not restrict dietary calcium intake 

**Medical:**

- Analgesia should be provided promptly
    - Non-steroidal anti-inflammatory drugs (NSAIDs) are first-line
    - Alternatives to the oral route (e.g. PR or IM diclofenac) may be required if patients are vomiting
    - IV paracetamol may be given if NSAIDs are contraindicated or insufficient
    - Opioid analgesia is the next step if neither of these are sufficient
- Medical expulsive therapy can be considered for patients with distal ureteric stones < 10mm 
    - This involves using an alpha-blocker (e.g. tamsulosin) to relax smooth muscle and promote passage of stones
- Patients with suspected infection secondary to renal stones should be treated urgently with IV antibiotics (e.g. gentamicin, co-amoxiclav)
- IV fluids may be required for patients dehydrated due to vomiting, decreased oral intake or infection
- Antiemetics may be required for vomiting
- Medical prophylaxis may be considered for recurrent stone formation
    - Potassium citrate is used for recurrent calcium oxalate stones
    - Thiazide diuretics may also be used for recurrent calcium oxalate stones 

**Surgical:**

- Patients with obstruction and hydronephrosis require urgent decompression with nephrostomy insertion
- Stenting is another option for ureteric obstruction
- Extracorporeal shockwave lithotripsy (ESWL)  refers to using high-energy shock waves to fragment a stone under fluoroscopic guidance
    - It can be used for stones < 2 cm in size and is first-line if < 1cm
    - It is contraindicated in pregnancy, coagulopathy and infection
- Ureteroscopy refers to retrieving stones endoscopically
    - First-line for ureteric stones 1-2 cm in size
    - Stenting may be offered in patients after retrieval of larger stones
- Percutaneous nephrolithotomy is used for renal stones > 2cm including complex stones such as staghorn calculi
    - It may also be used in smaller stones when other treatment approaches have failed
- Open stone surgery is rarely required but may be needed in complex cases or when other options have failed

# Complications

- **Obstruction** of the urinary tract by a stone leads to acute kidney injury and may cause irreversible renal impairment if not urgently decompressed
- **Infection** of an obstructed urinary system may be severe and life-threatening - pyelonephritis (upper urinary tract infection) and pyonephrosis (a buildup of pus in the kidney) may occur and there is a risk of sepsis
- **Ureteric strictures** may form if ureteric stones are not passed within a couple of weeks
- **Increased risk of renal cancers** (both renal cell carcinomas and upper tract urothelial carcinomas) is seen in patients with renal stones
- **Renal calyx rupture** is a rare complication and may lead to a urinoma (collection of urine in the abdomen)

# Prognosis

- 95% of stones < 5mm will pass spontaneously within 40 days
- 70% of distal ureteric stones (of all sizes) will pass spontaneously
- Rates of spontaneous passage are lower for more proximal stones (25% of proximal ureteric stones pass spontaneously)
- Recurrence rates are high - 80% at 10 years - although 50% of these people will only have one recurrence
- Frequent recurrence is seen in approximately 10% of patients
 
# NICE Guidelines

[NICE CKS - Renal or ureteric colic](https://cks.nice.org.uk/topics/renal-or-ureteric-colic-acute/)

[NICE - Renal and ureteric stones: assessment and management](https://www.nice.org.uk/guidance/ng118/)
 
# References

[Radiopaedia - Ureteric calculi](https://radiopaedia.org/articles/ureteric-calculi?lang=gb)

[Patient UK - Urinary tract stones](https://patient.info/doctor/urinary-tract-stones-urolithiasis)

[RCEM Learning - Renal colic](https://www.rcemlearning.co.uk/reference/renal-colic/)
"
839
884
Renal Stones and Renal Colic
Topic
22
Urology
10647
In patients with a single kidney and obstructive uropathy, prompt decompression via percutaneous nephrostomy is crucial to prevent renal deterioration.
A 43-year-old man presents with left-sided loin-to-groin pain. He has vomited twice. On examination, he appears to be in significant discomfort but his vital signs are within normal parameters. He is given a dose of diclofenac and a CT kidneys, ureters and bladder is performed. The CT scan reveals a left single kidney with a 30mm stone at the pelvico-ureteric junction and evidence of associated hydronephrosis. His blood tests are unremarkable.

What is the next best step in management?
a