Flank Pain and Temperature Conversion
Flank pain is pain located in the area between the lower ribs and the pelvis on either side of the back, typically indicating kidney or upper urinary tract pathology, and 38°C equals 100.4°F.
Definition of Flank Pain
Flank pain refers to discomfort in the lateral posterior region of the body between the lower ribs and the iliac crest. This anatomical location corresponds to the kidneys and upper ureters 1.
Clinical Significance
Flank pain serves as a key diagnostic indicator for upper urinary tract pathology, distinguishing conditions affecting the kidneys and ureters from lower urinary tract problems:
- Acute pyelonephritis typically presents with flank pain or tenderness, often accompanied by systemic symptoms such as fever, chills, malaise, and vomiting 1
- Urolithiasis (kidney stones) commonly causes flank pain due to ureteral hyperperistalsis when a stone passes through the ureter 2
- In children, pyelonephritis presents with flank pain along with high fever, malaise, vomiting, and abdominal tenderness 3
Diagnostic Context
The presence of flank pain helps clinicians differentiate between:
- Upper tract infections (pyelonephritis affecting kidneys and ureters) versus lower tract infections (cystitis affecting the bladder) 3
- Flank pain with fever and pyuria/bacteriuria makes acute pyelonephritis an appropriate presumptive diagnosis 1
- Up to 20% of pyelonephritis patients may lack bladder symptoms, making flank pain a critical diagnostic feature 1
Important caveat: Diabetic patients may not exhibit typical flank tenderness, making diagnosis more challenging 4.
Temperature Conversion
38°C = 100.4°F
This temperature represents a clinically significant fever threshold. While historical teaching suggested 98.6°F (37°C) as normal body temperature, more recent evidence indicates the upper limit of normal oral temperature is actually 99.9°F (37.7°C) in healthy adults 5.