Chronicles of an Inner City Hospital Resident Doctor #9

Hi everyone! I'm a 2nd year resident doctor in an inner city hospital. This is a blog to document some of the experiences I encounter as a training doctor, and some of the things that I learn in the process. After all, being a physician means that I'll be learning some fascinating topics for the rest of my career, and seeing how I can use those to help patients.

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Let's get started with today's topic, inspired by some reading I did today:

Diabetic Nephropathy

This article will actually be based on both readings and experience, because diabetic nephropathy is arguably the most common cause of chronic kidney disease worldwide. But what exactly is diabetic nephropathy? Let’s break it down: Nephropathy refers to kidney (nephro-) disease (-pathy), and kidney disease can be caused by many different things, one of the most common being diabetes, of which there are multiple different types. Thus, diabetic nephropathy is kidney disease caused by diabetes.

How does diabetes cause kidney disease? To understand this, we must understand how diabetes can cause damage to multiple organs and organ systems. While many people think of diabetes as a disease of high sugar, I tend to think of it as a vascular disease (in other words, a disease of the blood vessels). Why is this the case? Well, high blood sugar, which occurs frequently in diabetes, especially after carbohydrate-heavy meals, stress, or certain types of medications (corticosteroids), causes direct damage to the blood vessels. It does this directly, damaging the blood vessel wall and making it less elastic (i.e. rubber-band like) so that it cannot expand or contract as well; and indirectly, by combining with chemicals which cause the blood vessels to open wider. Thus, high sugar in the blood over a prolonged period of time will cause more damage to blood vessels. Blood vessels lead to every organ in the body, so that is how diabetes can cause pathologies in nearly every organ system in the body.

Thus, uncontrolled diabetes (where blood sugar is not well-controlled within a normal range), over the long term, will cause damage to the blood vessels within the kidneys. Since various parts of the kidney are deprived of oxygen and nutrients that they need to function properly, the kidneys get damaged over time. This leads to chronic kidney disease, which can be irreversible if the damage is chronic and not treated.

A drop of pathology and histology of diabetic nephropathy

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Without getting into excessive detail, the major pathologic findings from a biopsy of the kidney’s filtration system (the glomerulus) include 1) nodular mesangial expansion, thickened glomerular basement membrane, and arteriolar hyalinosis. In brief, the interaction of sugars with the matrix and fibers of the glomerulus cause the basement membrane and mesangium to become larger, and the arteriolar hyalinosis is a result of atherosclerosis due to hypertension and plaque buildup (which comes from chronic blood vessel damage). The mesangial nodules (also known as Kimmelsteil-Wilson nodules) develop when the mesangial expansion wraps around the tiny capillaries in the glomerulus.

The severity of diabetic nephropathy can be determined through the biopsy, but it’s not practical, and generally not useful, to obtain a biopsy from every person who has chronic kidney disease. We usually determine the severity of disease by how effectively the glomerulus filters blood, a value known as glomerular filtration rate (GFR). It measures how much blood passes through the kidneys, and it can be measured with a routine blood test which icidentally, also captures BUN an creatinine, two other markers of kidney function, as those are very commonly filtered products in the kidney.

A fun little tip: in some cases of people without kidney disease, the BUN and creatinine values can be slightly heightened. AN untrained eye can mistake those for developing or mild kidney disease, when in fact, the person just happens to be dehydrated! When there’s less fluid being filtered through the blood, these products sometimes appear more concentrated in the blood, so their levels in the blood are higher. Drinking some water brings their concentrations back to normal.

How is diabetic nephropathy treated?

A typical approach would be to treat both the underlying disease (diabetes) and the kidney itself. Chronic damage may be difficult to reverse, especially if it’s been developing for quite a few years.

Diabetes is typically treated with a combination of medications (commonly insulin, including long-acting and short-acting forms to keep the blood sugar steady throughout the day; other types are added if insulin is ineffective) and lifestyle modifications, including a decrease in carbohydrate-rich foods, an increase in exercise, and monitoring of blood sugar levels throughout the day. Progress is measured through changes in a value called HbA1c, which is an analog of the average of blood sugar levels over 3 months.

The kidney disease is often treated with intravenous fluids, which can help increase the volume of blood flowing through the kidney. As patients with uncontrolled diabetes tend to urinate more (this is the body’s mechanism of removing excess sugar from the blood), they are often dehydrated, which causes further damage to the kidneys due to lower blood flow. Thus, rehydration will help a larger volume of blood reach the kidneys, and not only will more blood reach the filtration system (glomerulus), so that it can receive oxygen and nutrients to function better, but more blood is filtered through the glomerulus itself. This all improves the GFR, BUN, and creatinine that we track in the bloodwork.

Kidney disease, of course, can become very complicated. There’s often an association of hypertension with kidney disease, in combination with diabetes, along with other comorbidities, and these affect our choice of medications. We’ll sometimes use antihypertensives (blood pressure medications) which are also shown to protect kidneys, such as ACE inhibitors; these have been shown to improve kidney function in patients with congestive heart failure. Of course, they have their own sets of side effects, so a lot of other factors are taken into consideration to determine the best treatment.

When medications don’t work, and the kidneys do not at all improve or continue to get worse, we may resort to a process known as hemodialysis, which acts as an external glomerulus / filtration system for the blood. Dialysis usually takes place between 3-7 days per week, for 2-3 hours at a time. Typically, once a person is placed on dialysis, they have to continue receiving it for the rest of their lives. There are more advanced forms of dialysis, and if those fail, the only remaining option is a kidney transplant – and that’s a whole other Pandora’s box of issues!

I hope you've enjoyed this little snippet of a topic I learned as a resident in an inner city hospital. I'll have many more stories and learning experiences coming in the future, so stay tuned.

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Disclaimer: this blog is for entertainment (and possibly educational) purposes only. This is not medical advice. If you have any questions or concerns about your own health, please contact a healthcare provider.

Here are the previous editions of this blog:
Chronicles of an Inner City Hospital Resident Doctor #8
Chronicles of an Inner City Hospital Resident Doctor #7
Chronicles of an Inner City Hospital Resident Doctor #6
Chronicles of an Inner City Hospital Resident Doctor #5
Chronicles of an Inner City Hospital Resident Doctor #4
Chronicles of an Inner City Hospital Resident Doctor #3
Chronicles of an Inner City Hospital Resident Doctor #2
Chronicles of an Inner City Hospital Resident Doctor #1