Coming soon, the bliss of summer: Sausages on the barbie, the tang of salt at the beach and … the excruciating wonder of kidney stones.

Summer is stone season. Why?

According to a 2018 paper, the body excretes a higher amount of calcium in the urine during winter.

This is thought to happen because we eat more salty, preserved and processed foods.

Higher sodium intake keeps calcium from being absorbed by the body. Instead it becomes just another waste product in urine.

Instead of passing out of the body, it can get stuck in the kidneys.  

When they form

It’s thought, then, that kidney stones begin forming in the winter months due to the body producing this excess calcium.

Complicit in this process is a mineral called oxalate that regulates calcium homeostasis, but in unhealthy quantities combines with calcium to form these stones.

Foods rich in oxalate include nuts, chocolate, spinach and tea – but eating loads of animal protein probably does more damage.

Phosphate can also bind with calcium and form stones.

Then, when summer hits, you tend to become more dehydrated – from the heat, but also from partying – and the formation of a kidney stone is accelerated.

Between four and eight per cent of the Australian population suffer from kidney stones at any time.

The risk of kidney stones is about one in 10 for men and one in 35 for women.

Kidney Health Australia says those odds are increased if you have a family history of kidney stones, or if you’re elderly.

According to 2017 advice for Australian GPs, upper urinary tract stones are a common problem in Australia: There’s a lifetime prevalence of up to 15 per cent in males and 8 per cent in females.

Four types of kidney stone

Kidney stones could be more accurately called kidney crystals.

They’re made up of different waste products that gather and stick together in the blood-cleaning process.

These hard, rock-like crystals have different sizes and shapes.

Some are as small as a grain of sand, others are, rarely, the size of a golf ball.

Often small stones pass out of the body unnoticed.

It’s probably the larger stones that led to the complaint that passing a stone is as painful as childbirth. There’s some evidence that this is occasionally true.

According to Kidney Health Australia, there are four main types of kidney stones:

• Calcium stones combined with oxalate or phosphate are the most common
• Struvite stones are often horn-shaped and quite large, mostly caused by urine infections
• Uric acid stones are often softer than other forms of kidney stones
• Cystine stones are rare and hereditary. They look more like crystals than stones.

Symptoms of kidney stones

Pain is usually the first sign.

This often occurs when the stone moves from where it was formed in the urinary tract.

You’ll typically experience a gripping pain in your back, just below your ribs. It can spread around to the front of your body, and sometimes towards your groin.

Other symptoms include:

• Blood in your urine
• Nausea and vomiting
• Shivers, sweating and fever, with cloudy or bad-smelling urine if there’s also an infection
• Small uric acid stones, which look like gravel, in your urine
• An urgent feeling of needing to urinate.

How to prevent kidney stones

According to the Mater Hospital Brisbane, if you have had a kidney stone in the past, “you are at a higher risk of developing more in the future, so prevention is very important”.

Mater says following these guidelines may assist you in preventing further kidney stones.

1. Drink plenty of fluids, especially water. This helps flush out the kidneys and dilute stone-forming substances. Aim for at least two litres of water in winter and three litres in summer, spread evenly throughout the day

2. Decrease salt intake. Salt increases the amount of calcium produced in your urine, which may result in stone formation.