Kidney Stones (Renal Calculi)

A patient with renal colic rarely looks comfortable. They may be pacing beside the trolley, leaning forward with a hand pressed into their flank, vomiting into a bowl and unable to find a position that settles the pain. Later, the scan may show a stone only a few millimetres across.

That can seem out of proportion until you stop thinking about the stone as a small hard object and start thinking about what it is doing to the urinary tract.

A kidney stone may sit quietly in the kidney. The pain usually begins when a stone enters the ureter and interferes with urine flow. From there, the anatomy, the pain, the investigations and the urgency of the nursing assessment all start to connect.

What is happening when a stone causes renal colic?

Urine contains water together with dissolved substances that the kidneys have filtered or secreted. Calcium, oxalate, uric acid and other salts are normally carried out of the body in solution. If urine becomes sufficiently concentrated, or the balance of substances within it favours crystallisation, crystals can begin to form. Some stay microscopic. Others grow or join together until a urinary stone develops.

Urolithiasis is the broad term for stones anywhere within the urinary tract. Nephrolithiasis refers to stones within the kidney. In practice, you will also hear renal stone and ureteric stone, because where the stone is sitting changes the clinical picture.

Calcium stones, particularly calcium oxalate, are the most common. Uric acid stones, infection-related struvite stones and cystine stones are other recognised types. Stone composition becomes especially relevant when somebody forms stones repeatedly because it can help guide investigation and prevention.

Low urine volume increases the concentration of stone-forming substances, but kidney stones should not be reduced to somebody simply “not drinking enough”. Diet, medicines, metabolic conditions, urinary infection, gastrointestinal disease, urinary tract anatomy and inherited disorders can all contribute. For some patients there will be more than one factor.

The pain becomes easier to understand when the stone moves from the kidney into the ureter. The ureter is a muscular tube that normally propels urine towards the bladder through coordinated contractions. If a stone obstructs that pathway, urine continues to arrive from the kidney but cannot drain normally. Pressure rises above the obstruction and the renal pelvis and ureter can become distended. At the same time, the ureter continues contracting as it tries to move the stone onwards.

Those changes stimulate visceral pain pathways and produce the severe, often wave-like pain of renal colic. It usually begins in the loin or flank and can move towards the lower abdomen and groin as the stone travels down the ureter. Nausea and vomiting are common. A stone rubbing against the urinary tract can also produce haematuria, although the absence of visible blood does not rule a stone out.

This is why a tiny stone can cause astonishing pain. The size of the object is not a direct measure of how much the patient will hurt. What matters clinically is where it is, how much it is obstructing, how acutely that obstruction has developed and what effect it is having on the kidney and the patient.

You may also see hydronephrosis described on imaging. Hydronephrosis is not another kind of stone. It means the collecting system of the kidney has become dilated because urine is not draining normally. In a patient with a ureteric stone, it can be a sign of obstruction upstream from the stone.

What should you notice at the bedside?

Renal colic can have a recognisable presentation, but severe flank or abdominal pain still needs assessment rather than an early label. Abdominal, vascular, gynaecological and other urinary conditions can present with pain in a similar region. The student nurse is not expected to make that diagnosis, but you do need to notice when the patient in front of you does not fit an uncomplicated picture.

Start with the pain itself. When did it begin? Where did it start and where is it travelling? Is it constant, colicky or changing? How severe is it, and what has already been given for it? Ask about nausea and vomiting, dysuria, urinary frequency or urgency and haematuria. Find out whether they have had stones before and whether they are still passing urine.

Then look beyond the pain score. Temperature, heart rate, blood pressure, respiratory rate, oxygen saturation and level of consciousness help you see whether this is a patient in severe pain who is otherwise physiologically stable, or a patient becoming systemically unwell. Use the local deterioration pathway and National Early Warning Score 2 (NEWS2) where applicable, but keep the wider clinical picture in view.

The history can alter the level of concern. Pregnancy changes the imaging pathway. A solitary functioning kidney makes obstruction more significant. Recurrent urinary tract infection, known renal disease, previous stones, relevant medicines and major comorbidities all belong in the assessment.

Urinalysis may show blood and may also raise suspicion of urinary infection. Depending on the presentation and local pathway, blood tests are commonly used to assess renal function and look for evidence of infection or other abnormalities. Urine culture may be needed when infection is suspected.

For a student nurse, the practical skill is to keep joining the findings together. Severe pain explains why the patient needs prompt analgesia. Reduced urine output makes you think about drainage. Fever and rigors change the level of concern. A rising creatinine suggests the kidneys are being affected. Persistent vomiting changes what the patient can tolerate and can contribute to dehydration. Each detail means more when you understand the urinary tract underneath it.

Imaging, pain relief and what treatment is trying to achieve

For adults with suspected renal colic, the National Institute for Health and Care Excellence (NICE) recommends urgent low-dose non-contrast computed tomography (CT) within 24 hours. In pregnancy, ultrasound is used instead. Children and young people should also have ultrasound first, with low-dose non-contrast CT considered if uncertainty remains.

The scan is not simply there to prove that the patient has a stone. It helps establish where the stone is, how large it is and whether it is causing obstruction. Those details influence whether the stone is likely to pass and whether urological intervention may be needed.

Pain relief should begin while that assessment is happening. NICE recommends a non-steroidal anti-inflammatory drug (NSAID), by any route, as first-line analgesia for suspected renal colic when it is appropriate for the patient. If an NSAID is contraindicated or has not provided enough relief, intravenous paracetamol can be offered. Opioids can be considered when both are unsuitable or have not controlled the pain. NICE advises against antispasmodics for renal colic.

That choice also fits the physiology: by inhibiting prostaglandin synthesis, NSAIDs reduce prostaglandin-mediated renal vasodilation and ureteric activity, helping to reduce pressure and pain during obstruction.

Once analgesia has been given, reassessment matters. Has the pain actually reduced? Is the patient still vomiting? Can they manage oral fluids when appropriate? Are they passing urine? Have their observations changed? A dose of analgesia should not close the assessment. Ongoing or escalating pain needs review.

If the patient is stable, infection is not suspected, renal function is satisfactory and the stone is suitable for conservative management, it may pass without a procedure. The chance of spontaneous passage depends largely on its size and position. For selected distal ureteric stones smaller than 10 mm, an alpha blocker may be considered to help stone passage, with prescribing guided by the clinical team and local medicines policy.

Some stones are unlikely to pass, or the patient remains in pain despite treatment. NICE recommends offering surgical treatment within 48 hours of diagnosis or readmission for adults with ureteric stones and renal colic when pain is ongoing and not tolerated or the stone is unlikely to pass.

The names of the procedures are easier to remember if you think about what each is trying to achieve. Shockwave lithotripsy (SWL) breaks a stone into smaller fragments using externally generated shock waves. Ureteroscopy passes a scope through the urethra and bladder into the ureter so the stone can be removed or fragmented, often with laser energy. Percutaneous nephrolithotomy (PCNL) reaches the kidney through a tract made through the back and is generally used for larger renal stone burdens.

A ureteric stent has a different purpose. It sits between the kidney and bladder to maintain drainage. A patient may therefore have a stent inserted before the stone itself has received definitive treatment. Restoring urine flow can be the immediate priority, with stone treatment planned later once the patient is stable.

Stents can themselves cause frequency, urgency, haematuria and flank or bladder discomfort. Those symptoms may be expected, but fever, systemic illness, worsening pain or deterioration should not be automatically attributed to the stent.

When obstruction and infection meet

This is where the same anatomy becomes much more urgent.

Imagine the ureter is obstructed and urine is collecting above the stone. If bacteria are also present, infected urine can become trapped within a system that cannot drain properly. The pressure remains, the infection has poor drainage and the patient can deteriorate rapidly.

An infected obstructed kidney is a urological emergency. Fever, rigors, hypotension, tachycardia, worsening renal function, reduced urine output, confusion or other signs of systemic illness alongside suspected urinary obstruction require urgent escalation.

Antibiotics are important, but an infected collection behind an obstruction may also need urgent drainage. This is why the urology team may insert a ureteric stent or arrange a percutaneous nephrostomy. Both provide a route for urine to leave the obstructed kidney. Definitive treatment of the stone can then be planned once the infection and the patient's condition have been addressed.

Anuria also changes the situation. If the patient is not passing urine, particularly where bilateral obstruction or obstruction of a solitary functioning kidney is possible, this needs urgent assessment. Waiting for the stone to “work its way out” is not an appropriate response to a kidney that may no longer be draining.

This is one of the most important distinctions in the whole topic. A stable patient with uncomplicated renal colic may be suitable for conservative management. A patient with obstruction and infection may need urgent source control as well as antimicrobial treatment. The stone may be the same kind of object, but the physiology around it is completely different.

After the acute episode

When the pain has settled and the immediate obstruction has been dealt with, attention shifts towards why the stone formed and how recurrence might be reduced.

NICE recommends considering stone analysis in adults and offering it to children and young people with renal or ureteric stones. Adults should also have serum calcium measured. Recurrent stones, unusual stone types or other clinical concerns may lead to more detailed metabolic investigation.

Long-term fluid advice is about reducing the concentration of stone-forming substances in urine, not forcing an acutely obstructing stone through the ureter. NICE advises adults to drink 2.5 to 3 litres of water each day as part of recurrence prevention, unless their clinical condition requires different fluid advice. Normal dietary calcium should generally be maintained rather than automatically restricted, and excessive salt intake should be avoided.

Prevention then becomes more individual. Stone composition, blood and urine results, diet, medicines and underlying conditions can all influence the plan. Some patients may need specialist dietary advice or medicines such as potassium citrate or a thiazide, depending on the type of stone and the metabolic findings.

For nursing practice, the important thread runs all the way back to the patient who arrived unable to sit still. The pain was not simply “because kidney stones hurt”. A stone entered a muscular ureter, urine flow became restricted, pressure developed above the obstruction and the urinary tract reacted.

That same explanation tells you what to keep looking for. Pain needs treating and reassessing. Urine output matters because it tells you something about drainage. Fever and rigors matter because infection behind an obstruction can become dangerous. Imaging matters because the size and position of the stone, and the effect on the urinary tract, change the management.

Once you can follow the stone through the urinary tract, renal colic stops being a list of symptoms to memorise. It becomes a patient whose anatomy and physiology are giving you clues about what is happening next.

References

British Association of Urological Surgeons (BAUS) Renal tract stones and renal colic.

National Institute for Health and Care Excellence (NICE) (2019) Renal and ureteric stones: assessment and management. NICE guideline NG118.

National Institute for Health and Care Excellence (NICE) (2020) Renal and ureteric stones. Quality standard QS195.

National Health Service (NHS) Kidney stones.