Catheter Occlusion or Thrombosis: This is the most common cause of dialysis catheter malfunction. Clotting or occlusion within the catheter can prevent the flow of blood, leading to its failure. The presence of a dialysis catheter increases the risk of thrombosis due to the foreign body reaction and blood flow alterations.

Catheter Malposition: The catheter might have become displaced from its original position, which could affect its function. This could happen due to movement, coughing, or other mechanical factors.
Kinking of the Catheter: Bending or kinking of the catheter can impede blood flow, leading to its malfunction. This is a common issue, especially if the catheter is not properly secured.
Infection: Although less likely to cause immediate cessation of function, infection can lead to catheter failure over time due to the formation of biofilms or thrombi.

Central Venous Thrombosis: While less common, a thrombosis in the central veins (such as the superior or inferior vena cava) can cause catheter malfunction and is a serious condition that requires prompt diagnosis and treatment to prevent severe complications.
Catheter-Related Septicemia: Infection leading to sepsis is a potentially life-threatening condition that requires immediate attention. Although it might not directly cause the catheter to stop working, it's a critical diagnosis not to miss due to its severity.

Catheter Fracture: Although rare, a fracture in the catheter can lead to its malfunction. This could be due to material fatigue or external trauma.
Vascular Stenosis: Narrowing of the veins due to scarring or other factors can impede blood flow through the catheter, leading to its failure. This is less common but should be considered, especially in patients with a history of long-term catheter use.
Fibrin Sheath Formation: A fibrin sheath can form around the catheter, potentially causing malfunction. This is a less common issue but can be a challenge to diagnose and treat.