The causes of haematuria are vast and can originate from any part of the urinary system. A systematic approach to diagnosis is essential, considering both common and rare etiologies. The underlying cause dictates the appropriate treatment and management strategy.

1. Infections of the Urinary Tract

Urinary tract infections (UTIs) are among the most common causes of haematuria, particularly in women, though they can affect anyone. These infections can affect the urethra (urethritis), the bladder (cystitis), or the kidneys (pyelonephritis).

• Cystitis: This is inflammation of the bladder, usually caused by a bacterial infection (most commonly *Escherichia coli*). Symptoms typically include frequent and painful urination (dysuria), a strong urge to urinate, suprapubic pain (pain in the lower abdomen), and sometimes gross haematuria. The bacterial infection and resulting inflammation irritate the delicate mucosal lining of the bladder, leading to capillary fragility and subsequent bleeding into the urine.
• Pyelonephritis: This is a more severe infection that has ascended from the lower urinary tract to affect one or both kidneys. Symptoms are typically more systemic and severe, including high fever, chills, nausea, vomiting, and severe flank pain, in addition to the classic UTI symptoms. The intense inflammation of the renal parenchyma (the functional tissue of the kidney) can lead to significant bleeding.
• Urethritis: Inflammation of the urethra, often caused by sexually transmitted infections such as Chlamydia or Gonorrhoea. While less common to cause gross haematuria, microscopic haematuria can frequently be present.

2. Urinary Tract Stones (Calculi)

Kidney stones (nephrolithiasis) and bladder stones (cystolithiasis) are a frequent and often painful cause of haematuria. These hard deposits form when certain chemicals in the urine, such as calcium, oxalate, or uric acid, become highly concentrated and crystallise.

• Mechanism of Bleeding: As these stones pass down the urinary tract, or even if they remain stationary but cause chronic irritation, their sharp edges can abrade the urothelium (the lining of the urinary tract). This mechanical trauma results in the release of red blood cells into the urine. The severity of haematuria can vary significantly, from microscopic to gross, often correlating with the size, jaggedness, and location of the stone, as well as the degree of surrounding inflammation.
• Associated Symptoms: Renal colic, characterised by excruciating, intermittent pain in the flank that often radiates to the groin or lower abdomen, is the classic presentation for kidney stones. Nausea, vomiting, and dysuria may also be present. Bladder stones can cause suprapubic pain, recurrent UTIs, and intermittent interruption of the urine flow.

3. Enlarged Prostate (Benign Prostatic Hyperplasia - BPH)

In men, particularly those over the age of 50, an enlarged prostate is a very common cause of haematuria. The prostate gland surrounds the urethra just below the bladder. As it grows with age—a condition known as Benign Prostatic Hyperplasia (BPH)—it can compress the urethra, leading to various urinary symptoms. However, BPH can also be a source of bleeding.

• Mechanism of Bleeding: The enlarged prostate often develops a rich blood supply with dilated, fragile blood vessels, particularly in the transitional zone of the gland. These vessels are prone to rupture, especially with straining during urination or minor trauma. Furthermore, the stretching and congestion of the prostatic urethra due to the obstruction can lead to mucosal tears and bleeding. Chronic inflammation within the prostate (prostatitis) can also contribute to haematuria.
• Associated Symptoms: BPH typically presents with lower urinary tract symptoms (LUTS) such as increased urinary frequency, urgency, nocturia (waking up multiple times at night to urinate), a weak urinary stream, hesitancy in starting urination, and a feeling of incomplete bladder emptying. Haematuria resulting from BPH is often intermittent and painless, although it can be exacerbated by physical activity or the use of certain medications.

4. Tumours of the Urinary Tract

Perhaps the most concerning cause of haematuria is malignancy within the urinary tract. Early detection is absolutely crucial for successful treatment and improved survival rates. Research indicates that the likelihood of a urological cancer in patients with non-visible haematuria increases significantly with age (particularly over 40), male sex, and a history of cigarette smoking [2].

• Bladder Cancer: This is the most common urinary tract cancer. Painless gross haematuria is the classic presenting symptom in approximately 80-90% of cases. The bleeding is often intermittent, which can unfortunately lead patients to delay seeking medical attention, mistakenly believing the issue has resolved. Other symptoms, such as irritative voiding symptoms (frequency, urgency, dysuria), may occur as the tumour grows or if it causes secondary inflammation. Studies have shown that patients presenting with gross haematuria are more likely to have a more advanced pathological stage of bladder cancer compared to those presenting with microscopic haematuria, underscoring the importance of early detection [3].
• Kidney Cancer (Renal Cell Carcinoma - RCC): Haematuria is a common symptom of kidney cancer, though it can be either microscopic or gross. The classic triad of symptoms—flank pain, a palpable abdominal mass, and haematuria—is now relatively rare, as most RCCs are detected incidentally on imaging performed for other reasons. Bleeding typically occurs when the tumour invades the collecting system of the kidney or develops fragile, neovascularised vessels that rupture.
• Ureteral and Renal Pelvic Cancers: These are rarer malignancies but can also present with haematuria, often accompanied by flank pain if the tumour causes an obstruction in the ureter.
• Prostate Cancer: While prostate cancer itself rarely causes haematuria directly in its early stages, advanced prostate cancer can invade the urethra or bladder, leading to bleeding. More commonly, haematuria in men with prostate cancer is due to co-existing BPH or other benign causes.

5. Other Less Common Causes

Beyond the primary categories, several other conditions can lead to haematuria:

• Glomerular Diseases: Conditions affecting the glomeruli (the kidney's microscopic filtering units), such as glomerulonephritis, can cause microscopic or sometimes gross haematuria. This is often accompanied by proteinuria (protein in the urine) and impaired kidney function. Examples include IgA nephropathy, post-infectious glomerulonephritis, and lupus nephritis.
• Trauma: Injuries to the kidneys, bladder, or urethra from accidents, falls, or sports can cause significant haematuria.
• Medications: Certain drugs, such as anticoagulants (e.g., warfarin, aspirin) and some chemotherapy agents, can increase the risk of bleeding in the urinary tract.
• Sickle Cell Trait/Disease: Individuals with sickle cell disease or trait can experience renal papillary necrosis, leading to haematuria.
• Exercise-Induced Haematuria: Strenuous exercise, particularly long-distance running, can sometimes cause transient haematuria due to renal microtrauma or increased glomerular permeability. This is usually benign but requires the exclusion of other causes.