What should you know about dark kidney stones?

A kidney stone is a solid mineral deposit formed in the urinary system. Its colour may vary with its chemical composition, age, blood staining or debris, so a dark appearance does not reveal whether it will pass easily or return. Kidney stones commonly cause severe, wave-like flank or abdominal pain, painful urination, nausea or blood in the urine, but symptoms vary. Dehydration can support stone formation and can also make urine darker. A stone that has been passed may be collected in a clean container for a clinician to examine.

Arrange a GP consultation if you suspect a stone, especially with flank pain, painful urination or blood in the urine. Drink fluids according to medical advice; forcing large amounts may be unsuitable if urine flow is blocked or you have another condition limiting fluids. Do not rely on colour to choose treatment. Keep any passed material dry and clean, and note the pain location, urine changes, vomiting, fever and whether urine flow is reduced. An abdominal ultrasound may be used to look for obstruction or other causes.

Seek urgent care for severe or uncontrolled pain, fever or chills with urinary symptoms, repeated vomiting, faintness, confusion, inability to pass urine, or a marked reduction in urine. These features can signal obstruction, infection or dehydration and should not be managed by waiting at home. Prompt assessment is also appropriate for visible blood in the urine or pain that is new, persistent or worsening.

Could the stone’s appearance suggest a composition that needs analysis? Do I need imaging such as an abdominal ultrasound? How should I manage fluids and pain, and which symptoms mean I should go straight to urgent care?