Pyelonephritis

Introduction

Pyelonephritis is defined as a severe inflammatory disease of the kidney, usually caused by an infection. Although it’s serious, I like to think the disease is actually kind of a qtt because its presentation is classically with the triad of QTT, queasiness and vomiting, tender flanks, and a high temperature.
You can classify Pyelonephritis as acute or chronic. Acute pyelonephritis is further classified into complicated or uncomplicated infection. We use uncomplicated to refer to cases where a non-pregnant female without anatomic abnormalities develops it. We make this distinction because outside this demographic, infection has been associated with more adverse outcomes.

Patient: Mr. John Smith

Age: 65

Sex: Male

Presenting Complaint:

Mr. Smith presents to the emergency department complaining of severe, tearing abdominal pain radiating to his lower back. He describes the pain as sudden in onset and progressively worsening over the past few hours. He denies any recent trauma but reports a history of hypertension and smoking for the past 30 years.

Clinical Assessment:

Upon examination, Mr. Smith appears pale and diaphoretic. His blood pressure is 160/100 mmHg, heart rate is 110 beats per minute, and respiratory rate is 22 breaths per minute. Abdominal examination reveals a pulsatile mass in the periumbilical region with tenderness on palpation. There are no signs of peritoneal irritation.

Diagnostic Workup:

Given the presentation suggestive of an abdominal aortic aneurysm, Mr. Smith undergoes urgent diagnostic imaging. A bedside ultrasound confirms the presence of a large abdominal aortic aneurysm measuring approximately 7 cm in diameter. Further imaging with a computed tomography (CT) scan of the abdomen confirms the diagnosis and provides detailed information about the extent and location of the aneurysm.

The actually pathogenesis of pyelonephritis is pretty simple. It most often develops as a result of an ascending urinary tract infection that often progresses from cystitis.

You must remember that the major causative pathogens are gram-negative bacteria, with E.coli causing approximately 80% of infections. Other common pathogens include Klebsiella especially in diabetics at 10%, and Proteus mirabilis at 5%.
However, in older hospitalised patients who tend to need catheters, other infections like Pseudomonas are much more common.

Additionally, obstruction of any cause including renal calculi or benign prostatic hyperplasia, often drive infection due to urinary stasis.

To investigate acute pyelonephritis in adults, consider a structured approach including bedside tests, bloods, and imaging.

Bed side tests should include urine dipstick, and urine microscopy, culture, and sensitivities.

Remember that the diagnosis of acute pyelonephritis is unlikely if pyuria is absent on microscopy.

Bloods should include blood cultures and some other basics include a FBC and UECs.

In terms of imaging, consider an ultrasound to exclude urinary obstruction or a kidney abscess. A contrast-enhanced CT or MRI should be performed if a patient remains febrile after 3 days or immediately if they’re deteriorating. Additional urological evaluation is usually required in men with pyelonephritis.

Treatment is really based on how sick a patient actually is.

A severe infection in adults requires IV antibiotics. This is defined as patients that have systemic symptoms like tachycardia, a fever, or if they have evidence of sepsis.

Empirical therapy might include IV gentamicin plus amoxicillin 2 g, 6-hourly. Alternatively, monotherapy with ceftriaxone 1g IV daily can be used.

In non-severe patients, oral antibiotic treatment might include oral amoxicillin+clavulanate, 12-hourly for 14 days.

Moving to its clinical features. Acute pyelonephritis almost universally causes flank pain which might be described as a pain in the lower back or under the ribs.

Palpable tenderness at the costovertebral angle is a key exam finding and can help differentiate the presentation from flank pain due to renal or ureteral stones.

A fever with a temperature over 38 degrees and other general signs of inflammation such as chills or malaise should raise concern.

Finally, nausea and sometimes vomiting are often associated with a kidney infection and might require anti-emetics. This is probably secondary to a systemic immune response.

Now, because it’s often secondary to cystitis from an ascending infection, pyelonephritis can, but not always, present with symptoms including dysuria, frequency, and urgency.

To remember the main cause of pyelonephritis, I remember that kidneys hate ecoli. This reminds me that 80% of infections are from this gram negative bacteria.

I also like keep in mind that pyelonephritis is a bit of a QTT, and presents with queasiness, tender flanks and a temperature.