Elevated Creatinine/Renal Failure is often seen as an abnormal lab finding in asymptomatic or symptomatic patients. Generally, a rise of 0.3 mg/dl in serum creatinine or a 1.5 times rise in creatinine from an individual’s baseline is considered to be renal dysfunction. Clinical presentation of renal failure can be divided into acute, sub-acute and chronic renal failure developing in less than 48 hours, between 48 hours and 3 months and over 3 months respectively. However, this timeline is arbitrary and clinical presentations may represent significant overlap. Additionally, patients with stable chronic renal failure may develop acute decompensation in renal function due to any of the several inciting factors and present acutely.

This clinical mind map is organized based upon pathologies arising from one of the three anatomical and functional areas around the renal system, which are 1. Pre-renal, 2. Renal and 3. Post-renal. The clinical mind map is organized this way because pathologies arising from these areas result in distinct constellation of symptoms and signs, and therefore can be distinguished from one another.  

Using the Epi-logical approach, a clinician must memorize the entire list of probable diagnoses. Then, the clinician must address urgent and emergent situations by looking at the patient’s vital signs and distress level. Regardless of the etiology, a clinician encounters an urgent or emergent situation when renal dysfunction has advanced to a degree sufficient enough to cause acutely life-threatening complications, such as uremic pericarditis, pleural effusion, and neurological complications. Acute electrolyte abnormalities such as acid base disturbance and hyperkalemia also pose urgent/emergent situations. A clinician may have difficulty in recognizing such situations based upon history or physical exam alone, unless an electrolyte abnormality or an acid base imbalance results in acute clinical decompensation. A quick evaluation to ensure that one of these complications has not set in can help address urgent or emergent situations.  

Next, the weighing process involves the reviewing of risk factors related to individual diagnoses, the gathering of information about specific or differentiating symptoms and signs, and finally removing the anchor bias, which involves making sure that certain diagnoses are not overlooked in a patient with obvious set of risk factors and clinical features which point to a specific diagnosis. An example is a patient with chronic hypertension and diabetes in whom a clinician suspects renal pathology and therefore is not surprised by a creatinine level of 1.4 mg/dl. A clinician might just focus on addressing and managing the original risk factors, which are hypertension and diabetes, but may ignore the new onset of obstructive symptoms, such as a weak urine stream, incomplete emptying, and night-time urinary frequency. In this case, a clinician may miss an obstructive pathology, such as prostate enlargement. This is an example of anchor bias that a clinician should remove.

Since this patient presentation consists of an abnormal lab finding, any additional lab results should be reviewed for the weighing process. This information includes FENA (fractional excretion of sodium), serum osmolality, urine osmolality and urinalysis, which provide tremendous value in terms of the weighing process. Features on urinalysis, such as the presence of casts and dysmorphic cells can help a clinician determine if an intrinsic renal/glomerular injury is or is not present. If and when such data is available, a clinician can refine history related questions to explore probable diagnoses which best match the lab and clinical data. This refinement of questions helps improve efficiency but should not be done at the cost of accuracy, which means addressing all likely diagnoses and removing anchor bias.

A few tips to remember diffferentials are;

Post and Pre-renal causes are intuitive. Renal causes are TANG ME with Cysts