The definition is in the name.

Morning report discussed a case of a patient who was initially admitted for mild volume overload that was treated appropriately in the standard fashion, but while in hospital, abnormalities were noted on the patient's laboratory investigations...

They included:

1. Rising creatinine

2. Rising phsophate

3. Dropping Calcium

4. Very elevated uric acid

Context helps, and the further information revealed that this patient has a history of a hematologic malignancy, that has been treated with aggressive, multi-modal chemotherapy, and unfortunately has recurred with signficant tumour burden.

Diagnosis......Tumour Lysis Syndrome.

Tumour Lysis Syndrome (TLS) is aptly named, and helps to understand the basic pathophys.

Tumour cells breakdown and release their intracellular contents, specifically K, UA, PO4, and as a result of the high PO4, binds and lowers Ca.

Thus there are laboratory criteria for TLS, essentially being:

1. Hyperkalemia

2. Hyperuricemia

3. Hyperphosphatemia

4. Hypocalcemia.

Clinical criteria, are essentially all the downstream problems that the above can cause, with the big categories being:

1. AKI (think about calcium, UA, possibly xanthine precipitation)

2. Cardiac (dysrhytmias from K and Ca abnormalities)

3. Neuro (tetany, seizures)

TLS also can lead to a general inflammatory "SIRS" like reaction that can contribute to multi-organ failure.

Risk Factors for TLS include

1. Type of cancer (usually hematologic, rapidly progressive, but now noticing in other cancers previously thought to be rare).

2. Tumour burden (ie mets, bulk).

3. Treatment factors: highly aggressive, rapid cell turnover treatment 

4. Patient factors: do they have underlying kidney disease, hypovolemia, etc.?

5. MD factors: did we prophylax, give fluids

Priniciples of management:

1. Fluids, fluids, fluids

2. Excretion: whether through agents such as rasburicase (that facilitate excretion by converting UA to allantoin. Remember that allopurinol only inhibits formation of more UA, but does not mediate excretion.

Diuretics can be used. Dialysis often considered in severe cases. 

See this 2011 review article from the NEJM for more details.