January 11, 2025

Curvilicious

In this post… The Brenner hypothesis Tubuloglomerular feedback & glomerulotubular balance How SGLT2i affect glomerular haemodynamics How loop diretics effect glomerular haemodynamics The importance of intraglomerular pressure At the cornerstone of contemporary treatments to delay CKD progression are agents (RAS inhibitors and SGLT2i) that reduce intraglomerular pressure. Whether or not this effect is the most important mechanism of nephroprotection is open to debate - particularly for SGLT2i. However, it is at the very least likely to be a central mechanism.

January 10, 2025

Bicarbonaturia

In this post… The renal regulation of bicarbonate excretion The pathogenesis of proximal RTA The pathophysiology of vomiting How is renal bicarbonate excretion regulated? With respect to bicarbonate reabsorption, there are two key parameters to consider: the Tm = maximal rate of tubular HCO3 reabsoption and the renal bicarbonate threshold = the serum [HCO3] at which the filtered load exceeds Tm, and bicarbonate begins to appear in the urine.

January 27, 2023

A tonic for hyponatraemia

In this post… The etymology of “tonic”. Is urea an effective osmole? The anatomy of the EFWC equation. How do NaCl supplements help in hyponatraemia? tonic, adj. and n. Medicine, etc. Having the property of increasing or restoring the tone or healthy condition and activity of the system or organs; strengthening, invigorating, bracing. (Of remedies or remedial treatment, and hence of air, climate, etc.) Etymology: Greek of or for stretching

January 27, 2022

Dietary salt: clinical pearls

In this post… A summary of our recent salt perspectives paper A few “clinical pearls” relating to salt Introduction We (with Matt Bailey and Bean Dhaun) recently wrote a perspectives article on salt and disease. This was an entertaining and educational process. Here I reflect on what I learned while writing the review, expanding a little on some potentially useful “clinical pearls”. (As the following is discussed in detail and fully referenced in our paper, I have not inserted many references below.

August 13, 2021

The E=mc2 of nephrology

In this post… Why drinking seawater causes dehydration Why giving 0.9% NaCl can exacerbate hyponatraemia in some circumstances How much water do you have to drink to cause hyponatraemia Why most patients on furosemide should also have restricted water intake Why a “tea and toast” diet causes hyponatraemia Why limiting dietary solute intake can help in nephrogenic diabetes insipidus Physicists may still be searching for the grand unified theory of everything, but nephrologists have come pretty close to a unified theory of urine.

August 2, 2021

When is a diuretic not a diuretic?

In this post… The paradoxical anti-diuretic effects of diuretics A general approach to nephrogenic diabetes insipidus When is a tractor not a tractor? … When it turns into a field Nephrogenic diabetes insipidus Nephrologists are often asked for advice on how to manage patients with nephrogenic diabetes insipidus (NDI). Almost always, this has been caused by current or historic lithium exposure. This is one of those referrals that invariably sends me scuttling back to review original literature, because I can never quite remember how on earth diuretics are supposed to magically transform into anti-diuretics in this context, nor the relative merits of thiazides / amiloride / acetazolamide.

September 21, 2020

Oh Mg (part 2)

In this post… Why does low Mg cause low K? Distal Na and K transport and the transepithelial voltage Hypomagnesaemia: easy to find if you go looking for it; usually left well alone. (And often caused by a drug.) But sometimes hypomagnesaemia is worth paying attention to if it is contributing to another electrolyte disorder such as hypocalcaemia or hypokalaemia. Any medical student can tell you that Mg deficiency can cause refractory hypokalaemia.

June 16, 2020

How to assess free water balance in dysnatraemia

In this post… How to assess free water balance in the dysnatraemias How to factor in solute / cation balance “There’s more than one way to skin a cat.” — Proverb So the proverb goes. But that is only because whoever came up with the proverb back in the 19th century had never attempted to assess free water balance in a case of hyponatraemia. More than any other electrolyte disorder, hyponatraemia has the capacity to become unneccessarily complicated.