Enhancing Sepsis Care with Analytics (Part 2) : Exploring BUN Trends, Kidney Stress and Clinical Pathways
After analyzing MAP Biomarker for Sepsis Analysis in my "Enhancing Sepsis Care with Analytics (Part 1): Exploring Mean Arterial Pressure (MAP) and Clinical Pathways" blog. You can go through that by this link https://www.numpyninjaacademy.com/post/enhancing-sepsis-care-with-analytics-part-1-exploring-mean-arterial-pressure-map-and-clinical.
We are now analyzing other biomarkers. In this blog we are going with how BUN Biomarker affects Kidney in Sepsis. BUN is such a clean way to watch the kidney struggle in sepsis.
Before starting with our analysis lets get to know about the BUN and Kidneys are affected in sepsis.
BUN refers to a Blood Urea Nitrogen, Its common blood test that measures the amount of urea nitrogen (a waste product from protein breakdown) in your blood to check how well your kidneys and liver are functioning.
In Sepsis Kidney organ is severely impacted, often causing Acute Kidney Injury (AKI), a common and serious complication where kidneys fail to filter waste, leading to organ dysfunction and higher death risk. If the patient have existing kidney condition they will be more vulnerable for the sepsis as their immune system is weak. They can have stage 3 sepsis in very short time period.
Now Lets start with our Analysis Average BUN Levels by Kidney Stage and Gender
In the above Lollipop chart, we assigned each patient a stage based on their average Blood Urea Nitrogen (BUN). This gives a more stable view for kidney stress. We used the following thresholds which I have calculated by BUN levels.
Normal- Patients with an average BUN below 20 mg/dL were classified as having no significant kidney dysfunction.
Stage 1 (Risk)- Patients with average BUN between 20 and 30 mg/dL were flagged as at risk for kidney injury.
Stage 2 (Injury)- Patients with average BUN between 30 and 50 mg/dL were considered to have AKI.
Stage 3 (Failure)- Patients with average BUN above 50 mg/dL were classified as having severe kidney failure.
By analyzing the chart we see that-
Normal kidney stage - Female at 13 and Male at 12.These BUN levels are what we expect in healthy kidney function. The kidneys are filtering waste normally, and there’s no sign of stress or injury.
Stage 1 Risk - Female at 24 and Male at 24. BUN has almost doubled compared to normal. This suggests the kidneys are starting to struggle, showing the first signs of sepsis‑related stress.
Stage 2 – Injury Female at 38 and Male at 38. BUN is now clearly elevated. This means the kidneys are injured and not filtering waste well. In sepsis, this usually reflects acute kidney injury (AKI).
Stage 3 – Failure Female at 74 and Male at 72. These are very high BUN levels. The kidneys are in severe failure, unable to clear toxins from the blood.
In the next chart BUN-Based Kidney Stage by ICU Stay: Sepsis vs Non-Sepsis
In this butterfly chart we are further analyzing how bun affects sepsis patients in their ICU stay. We categorized ICU stay in “Short Stay” patients that stayed not more than 3 days, “Moderate Stay” patients that stayed for 4 to 7 days and “Prolonged Stay” patients that stayed for more than 7 days having Non Sepsis and Sepsis on left and right side. Colors shows the different Kidney stages red the Stage 3 and green normal which I have calculated using BUN level and its range is mentioned in above.
By analyzing the above chart we get that-
Non-Sepsis patients maintain more balanced kidney function, with most remaining in the Normal or Risk stages. Around 20000 patients fall in the Normal stage and Around 5000 patients are in Stage 3. It clearly shows that Kidney failure is not severe in non sepsis.
Sepsis patients show strikingly more patients in kidney failure Stage 3 across all ICU stay duration even in short ICU stay. Though the patient count is very less as compared to non sepsis patients. Even these sepsis patients staying ICU most are admitted due to Stage 3. It clearly shows how severe and threatening BUN level rise affects the kidney.
Last chart the Correlation of BUN with Creatinine, Phosphate, Lactate, Bilirubin Biomarkers
Now in this BUN biomarker series the last chart is the correlation chart where I am comparing BUN with other 5 biomarkers. Each subplot shows a scatter plot with trend lines for three groups sepsis, non sepsis and onset.
In above correlation chart, After analyzing all five biomarkers we get that -
1. BUN vs Creatinine plot- Creatinine is a waste product that rises when the kidneys can’t filter properly. The plot shows strong correlation as creatinine rises, BUN rises especially in sepsis patients (red line). This shows that both markers reflect kidney dysfunction and strong link confirms worsening sepsis.
2. BUN vs Phosphate plot - Phosphate is a mineral that builds up when the kidneys are injured. Higher phosphate levels tend to go with higher BUN, especially in sepsis a strong correlation.
3. BUN vs Lactate plot - Lactate is a marker of low oxygen and body stress during severe. It shows downward trend, suggesting that correlation is weak.
4. BUN vs Bilirubin plot - Bilirubin is liver waste product that increases when the liver is stressed or damaged. There's downward trend between BUN and bilirubin in sepsis. And for non sepsis and onset its upward. It shows that they are not correlated in sepsis.
5. BUN vs Glucose plot - Glucose is the sugar level in the blood that reflects energy balance and stress response. BUN doesn’t show a clear pattern with glucose. This means kidney stress is not affected by glucose levels.
Limitations
BUN can rise for reasons other than kidney injury. The sepsis group is much smaller compared to non sepsis group and for correlations we have to consider other biomarkers also. BUN alone cannot tell the full story.
Conclusion
All three charts show the same clear message: BUN goes up when the kidneys are stressed or failing, and this happens much more in sepsis patients. The first chart shows BUN rising step‑by‑step from normal kidneys to complete kidney failure. The second chart shows that sepsis patients, no matter how long they stay in the ICU, have many more cases of severe kidney failure compared to non‑sepsis patients. The third chart shows that when BUN goes up, other kidney‑related markers like creatinine and phosphate also go up, proving the kidneys are not working well. Together, these charts tell us that BUN is a strong and reliable sign of kidney damage in sepsis,
Overall, BUN becomes a reliable marker to kidney injury, track worsening organ stress, and identify patients who need closer monitoring. If we can detect early kidney involvement in sepsis we can give better Healthcare treatment.
